What I am doing wrong?

07:59:19,562 ERROR [GraphElement] action threw exception: couldn't evaluate expression '#{treeBacker.createTomahawkTreeModel}'
org.jbpm.JbpmException: couldn't evaluate expression '#{treeBacker.createTomahawkTreeModel}'
 at org.jbpm.jpdl.el.impl.JbpmExpressionEvaluator.evaluate(JbpmExpressionEvaluator.java:38)
 at org.jbpm.graph.def.Action.execute(Action.java:119)
 at org.jbpm.graph.def.GraphElement.executeAction(GraphElement.java:235)
 at org.jbpm.graph.def.GraphElement.executeActions(GraphElement.java:212)
 at org.jbpm.graph.def.GraphElement.fireAndPropagateEvent(GraphElement.java:182)
 at org.jbpm.graph.def.GraphElement.fireEvent(GraphElement.java:166)
 at org.jbpm.graph.def.Transition.take(Transition.java:106)
 at org.jbpm.graph.def.Node.leave(Node.java:383)
 at org.jbpm.graph.exe.Token.signal(Token.java:174)
 at org.jbpm.graph.exe.Token.signal(Token.java:137)
 at org.jbpm.graph.exe.ProcessInstance.signal(ProcessInstance.java:229)
 at org.jboss.seam.pageflow.PageflowHelper.signal(PageflowHelper.java:47)
 at org.jboss.seam.core.Pageflow.navigate(Pageflow.java:298)
 at org.jboss.seam.jsf.SeamNavigationHandler.handleNavigation(SeamNavigationHandler.java:30)
 at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:84)
 at javax.faces.component.UICommand.broadcast(UICommand.java:106)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.processEvents(AjaxViewRoot.java:274)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.broadcastEvents(AjaxViewRoot.java:250)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.processApplication(AjaxViewRoot.java:405)
 at org.apache.myfaces.lifecycle.LifecycleImpl.invokeApplication(LifecycleImpl.java:343)
 at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:86)
 at javax.faces.webapp.FacesServlet.service(FacesServlet.java:137)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:144)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:75)
 at org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:213)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at cz.proj.om.service.filters.AuthorizationFilter.doFilter(AuthorizationFilter.java:76)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
 at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
 at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
 at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
 at java.lang.Thread.run(Thread.java:595)
Caused by: javax.ejb.EJBNoSuchObjectException: Could not find Stateful bean: 5c4o51i-esl8po-f17c5bed-1-f17d52bc-q
 at org.jboss.ejb3.cache.simple.SimpleStatefulCache.get(SimpleStatefulCache.java:268)
 at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:61)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:77)
 at org.jboss.ejb3.security.Ejb3AuthenticationInterceptor.invoke(Ejb3AuthenticationInterceptor.java:102)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:47)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.stateful.StatefulContainer.localInvoke(StatefulContainer.java:203)
 at org.jboss.ejb3.stateful.StatefulLocalProxy.invoke(StatefulLocalProxy.java:98)
 at $Proxy280.createTomahawkTreeModel(Unknown Source)
 at cz.proj.TomahawkTreeBackerLocalIF$$FastClassByCGLIB$$f29f9cf2.invoke(<generated>)
 at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
 at org.jboss.seam.intercept.RootInvocationContext.proceed(RootInvocationContext.java:45)
 at org.jboss.seam.intercept.ClientSideInterceptor$1.proceed(ClientSideInterceptor.java:74)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:55)
 at org.jboss.seam.interceptors.RemoveInterceptor.removeIfNecessary(RemoveInterceptor.java:40)
 at sun.reflect.GeneratedMethodAccessor150.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
 at org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
 at org.jboss.seam.interceptors.SynchronizationInterceptor.serialize(SynchronizationInterceptor.java:31)
 at sun.reflect.GeneratedMethodAccessor149.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
 at org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
 at org.jboss.seam.intercept.RootInterceptor.createSeamInvocationContext(RootInterceptor.java:144)
 at org.jboss.seam.intercept.RootInterceptor.invokeInContexts(RootInterceptor.java:129)
 at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:102)
 at org.jboss.seam.intercept.ClientSideInterceptor.interceptInvocation(ClientSideInterceptor.java:83)
 at org.jboss.seam.intercept.ClientSideInterceptor.intercept(ClientSideInterceptor.java:52)
 at org.jboss.seam.intercept.Proxy$$EnhancerByCGLIB$$e2c1cb43.createTomahawkTreeModel(<generated>)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jbpm.jpdl.el.impl.BeanMethod.invoke(BeanMethod.java:19)
 at org.jbpm.jpdl.el.impl.ArraySuffix.evaluate(ArraySuffix.java:287)
 at org.jbpm.jpdl.el.impl.ComplexValue.evaluate(ComplexValue.java:146)
 at org.jbpm.jpdl.el.impl.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:264)
 at org.jbpm.jpdl.el.impl.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:191)
 at org.jbpm.jpdl.el.impl.JbpmExpressionEvaluator.evaluate(JbpmExpressionEvaluator.java:34)
 ... 51 more
07:59:19,687 ERROR [[Faces Servlet]] Servlet.service() for servlet Faces Servlet threw exception
org.jbpm.graph.def.DelegationException
 at org.jbpm.graph.def.GraphElement.raiseException(GraphElement.java:352)
 at org.jbpm.graph.def.GraphElement.raiseException(GraphElement.java:346)
 at org.jbpm.graph.def.GraphElement.executeAction(GraphElement.java:249)
 at org.jbpm.graph.def.GraphElement.executeActions(GraphElement.java:212)
 at org.jbpm.graph.def.GraphElement.fireAndPropagateEvent(GraphElement.java:182)
 at org.jbpm.graph.def.GraphElement.fireEvent(GraphElement.java:166)
 at org.jbpm.graph.def.Transition.take(Transition.java:106)
 at org.jbpm.graph.def.Node.leave(Node.java:383)
 at org.jbpm.graph.exe.Token.signal(Token.java:174)
 at org.jbpm.graph.exe.Token.signal(Token.java:137)
 at org.jbpm.graph.exe.ProcessInstance.signal(ProcessInstance.java:229)
 at org.jboss.seam.pageflow.PageflowHelper.signal(PageflowHelper.java:47)
 at org.jboss.seam.core.Pageflow.navigate(Pageflow.java:298)
 at org.jboss.seam.jsf.SeamNavigationHandler.handleNavigation(SeamNavigationHandler.java:30)
 at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:84)
 at javax.faces.component.UICommand.broadcast(UICommand.java:106)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.processEvents(AjaxViewRoot.java:274)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.broadcastEvents(AjaxViewRoot.java:250)
 at org.ajax4jsf.framework.ajax.AjaxViewRoot.processApplication(AjaxViewRoot.java:405)
 at org.apache.myfaces.lifecycle.LifecycleImpl.invokeApplication(LifecycleImpl.java:343)
 at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:86)
 at javax.faces.webapp.FacesServlet.service(FacesServlet.java:137)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:144)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.ajax4jsf.framework.ajax.xmlfilter.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:75)
 at org.ajax4jsf.framework.ajax.xmlfilter.BaseFilter.doFilter(BaseFilter.java:213)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at cz.proj.om.service.filters.AuthorizationFilter.doFilter(AuthorizationFilter.java:76)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
 at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
 at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
 at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
 at java.lang.Thread.run(Thread.java:595)
Caused by: org.jbpm.JbpmException: couldn't evaluate expression '#{treeBacker.createTomahawkTreeModel}'
 at org.jbpm.jpdl.el.impl.JbpmExpressionEvaluator.evaluate(JbpmExpressionEvaluator.java:38)
 at org.jbpm.graph.def.Action.execute(Action.java:119)
 at org.jbpm.graph.def.GraphElement.executeAction(GraphElement.java:235)
 ... 49 more
Caused by: javax.ejb.EJBNoSuchObjectException: Could not find Stateful bean: 5c4o51i-esl8po-f17c5bed-1-f17d52bc-q
 at org.jboss.ejb3.cache.simple.SimpleStatefulCache.get(SimpleStatefulCache.java:268)
 at org.jboss.ejb3.stateful.StatefulInstanceInterceptor.invoke(StatefulInstanceInterceptor.java:61)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:77)
 at org.jboss.ejb3.security.Ejb3AuthenticationInterceptor.invoke(Ejb3AuthenticationInterceptor.java:102)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:47)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:106)
 at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:101)
 at org.jboss.ejb3.stateful.StatefulContainer.localInvoke(StatefulContainer.java:203)
 at org.jboss.ejb3.stateful.StatefulLocalProxy.invoke(StatefulLocalProxy.java:98)
 at $Proxy280.createTomahawkTreeModel(Unknown Source)
 at cz.proj.TomahawkTreeBackerLocalIF$$FastClassByCGLIB$$f29f9cf2.invoke(<generated>)
 at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
 at org.jboss.seam.intercept.RootInvocationContext.proceed(RootInvocationContext.java:45)
 at org.jboss.seam.intercept.ClientSideInterceptor$1.proceed(ClientSideInterceptor.java:74)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:55)
 at org.jboss.seam.interceptors.RemoveInterceptor.removeIfNecessary(RemoveInterceptor.java:40)
 at sun.reflect.GeneratedMethodAccessor150.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
 at org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
 at org.jboss.seam.interceptors.SynchronizationInterceptor.serialize(SynchronizationInterceptor.java:31)
 at sun.reflect.GeneratedMethodAccessor149.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jboss.seam.util.Reflections.invoke(Reflections.java:18)
 at org.jboss.seam.intercept.Interceptor.aroundInvoke(Interceptor.java:169)
 at org.jboss.seam.intercept.SeamInvocationContext.proceed(SeamInvocationContext.java:64)
 at org.jboss.seam.intercept.RootInterceptor.createSeamInvocationContext(RootInterceptor.java:144)
 at org.jboss.seam.intercept.RootInterceptor.invokeInContexts(RootInterceptor.java:129)
 at org.jboss.seam.intercept.RootInterceptor.invoke(RootInterceptor.java:102)
 at org.jboss.seam.intercept.ClientSideInterceptor.interceptInvocation(ClientSideInterceptor.java:83)
 at org.jboss.seam.intercept.ClientSideInterceptor.intercept(ClientSideInterceptor.java:52)
 at org.jboss.seam.intercept.Proxy$$EnhancerByCGLIB$$e2c1cb43.createTomahawkTreeModel(<generated>)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.jbpm.jpdl.el.impl.BeanMethod.invoke(BeanMethod.java:19)
 at org.jbpm.jpdl.el.impl.ArraySuffix.evaluate(ArraySuffix.java:287)
 at org.jbpm.jpdl.el.impl.ComplexValue.evaluate(ComplexValue.java:146)
 at org.jbpm.jpdl.el.impl.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:264)
 at org.jbpm.jpdl.el.impl.ExpressionEvaluatorImpl.evaluate(ExpressionEvaluatorImpl.java:191)
 at org.jbpm.jpdl.el.impl.JbpmExpressionEvaluator.evaluate(JbpmExpressionEvaluator.java:34)
 ... 51 more