I decided to leave the rule and try other process without rule,
the process is located on different Guvnor package and this process does not have any Business Rule Task Node
Surprisingly I still got error and the Null Pointer Exception comes from the rule that is stored in different package.
So I can use my jbpm to start process again only after I delete all rules in Guvnor.
Why even rule that not related to a process still get executed?
Regards,
Thomas Setiabudi