JPAWorkItemManager.internalAbortWorkItem fails with NPE

The NullPointerException occurs at line 63 of JPAWorkItemManager and can only be because workItems is null at that point. Which I think is to be expected as an existing session was loaded from the database in order to abort a process instance and the workItems property is transient. There shouldn't even be a workItems property in this class. At least the remove should be guarded with if (workItems != null) as it is done elsewhere in the same class.
Regards,
Johan