NPE when AbortWorkItem

AbortWorkItem method should test if WorkItemInfo inst null before merge. Basically is the same behaviour as completeWorkItem.

I'm getting the following exception when a Work Item is aborted:

2011-02-10 16:52:37,282 ERROR [org.drools.persistence.SingleSessionCommandService] (NioProcessor-3) Could not commit session
java.lang.IllegalArgumentException: attempt to create merge event with null entity
at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:60)
at org.hibernate.event.MergeEvent.<init>(MergeEvent.java:43)
at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:690)
at org.hibernate.impl.SessionImpl.merge(SessionImpl.java:694)
at org.hibernate.ejb.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:235)
at org.drools.persistence.jpa.JpaPersistenceContext.merge(JpaPersistenceContext.java:49)
at org.drools.persistence.jpa.processinstance.JPAWorkItemManager.abortWorkItem(JPAWorkItemManager.java:136)
at org.drools.command.runtime.process.AbortWorkItemCommand.execute(AbortWorkItemCommand.java:56)
at org.drools.command.runtime.process.AbortWorkItemCommand.execute(AbortWorkItemCommand.java:29)
at org.drools.persistence.SingleSessionCommandService.execute(SingleSessionCommandService.java:295)
at org.drools.command.impl.CommandBasedStatefulKnowledgeSession$1.abortWorkItem(CommandBasedStatefulKnowledgeSession.java:152)
at org.jbpm.process.workitem.wsht.CommandBasedWSHumanTaskHandler$GetCompletedTaskResponseHandler.execute(CommandBasedWSHumanTaskHandler.java:245)
at org.jbpm.task.service.TaskClientHandler.messageReceived(TaskClientHandler.java:81)
at org.jbpm.task.service.mina.MinaTaskClientHandler.messageReceived(MinaTaskClientHandler.java:47)