BusinessCalendarImpl throws null pointer exception

[joshsiaw]

=== Environment ==============================
- jBPM Version : 4.2
- Database : MySql 5.0.67
- JDK : 1.6.0_16
- Container : 1.6.0_16
- Configuration : default jbpm.cfg.xml copied from Examples project
- Libraries : default jBPM 4.2 libraries

=== Process ==================================

<?xml version="1.0" encoding="UTF-8"?>

<process name="test" xmlns="http://jbpm.org/4.0/jpdl">
 <start g="193,63,48,48" name="start1">
 <transition to="Inspection"/>
 </start>
 <task assignee="valTech1" g="170,141,92,52" name="Inspection" duedate="10 business hours">
 <transition to="Verify Inspection Report" name="timeout" g="11,-7">
 </transition>
 </task>
 <task assignee="svt" g="147,224,136,52" name="Verify Inspection Report">
 <transition to="Valuation"/>
 </task>
 <task assignee="avo" g="171,316,92,52" name="Valuation">
 <transition to="Certify Valuation"/>
 </task>
 <task assignee="vo" g="165,397,106,52" name="Certify Valuation">
 <transition to="Billing"/>
 </task>
 <task assignee="clerk" g="173,478,92,52" name="Billing">
 <transition to="end1"/>
 </task>
 <end g="194,558,48,48" name="end1"/>
</process>

=== API ===================================

Task task = jbpmServices.getTaskService().createTaskQuery().processDefinitionId("test-1").activityName("Inspection").uniqueResult();
Calendar cal = Calendar.getInstance();
BusinessCalendarImpl businessCalendar = new BusinessCalendarImpl();
Duration duration = new Duration("10 business days");
Date date = businessCalendar.add(cal.getTime(), duration);
task.setDuedate(date);

=== Stacktrace ==============================

Exception in thread "main" java.lang.NullPointerException
at org.jbpm.pvm.internal.cal.BusinessCalendarImpl.findDay(BusinessCalendarImpl.java:154)
at org.jbpm.pvm.internal.cal.BusinessCalendarImpl.findDayPart(BusinessCalendarImpl.java:160)
at org.jbpm.pvm.internal.cal.BusinessCalendarImpl.add(BusinessCalendarImpl.java:78)
at eval.tester.tester.testTaskDueDate(tester.java:56)
at eval.tester.tester.main(tester.java:39)

=== Debug logs ==============================

Fails at this point:

protected Day findDay(Date date) {
 Calendar calendar = createCalendar();
 calendar.setTime(date);
 int weekDayIndex = calendar.get(Calendar.DAY_OF_WEEK);
 return days[weekDayIndex];
 }

=== Problem description =========================

BusinessCalendarImpl throws null pointer exception. Looking through the code it looks like its caused by the days[] being null. Am I using it correctly? Any help would be appreciated.