Hi, I am trying to use jsFunction but getting this error:

java.lang.StringIndexOutOfBoundsException: String index out of range: 0
     at java.lang.String.charAt(String.java:686)
     at org.ajax4jsf.context.AjaxContextImpl.convertId(AjaxContextImpl.java:388)
     at org.ajax4jsf.context.AjaxContextImpl.addRegionsFromComponent(AjaxContextImpl.java:331)
     at org.ajax4jsf.component.AjaxActionComponent.setupReRender(AjaxActionComponent.java:96)
     at org.ajax4jsf.component.AjaxActionComponent.broadcast(AjaxActionComponent.java:60)
     at org.ajax4jsf.component.AjaxViewRoot.processEvents(AjaxViewRoot.java:321)
     at org.ajax4jsf.component.AjaxViewRoot.broadcastAjaxEvents(AjaxViewRoot.java:340)
     at org.ajax4jsf.application.AjaxViewHandler.processAjaxEvents(AjaxViewHandler.java:216)
     at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:169)
     at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110)
     at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
     at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
     at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83)
     at org.jboss.seam.web.RewriteFilter.doFilter(RewriteFilter.java:63)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:90)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:178)
     at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290)
     at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:368)
     at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:495)
     at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:60)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at com.snaptale.ui.view.util.SessionIdFilter.doFilter(SessionIdFilter.java:75)
     at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69)
     at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
     at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
     at java.lang.Thread.run(Thread.java:619)

Page code:

            <a4j:jsFunction name="update" reRender="" action="#{myBean.action}">
        </a4j:jsFunction>

in my bean:

  public void action()
  {
    System.out.println("action!");
  }

Any idea?