[rules-users] Ascending sort by salience results in NPE

[Wolfgang Laun]

rule "process Token"
salience  - $prio   // by ascending x25No values
when
    $token: Token( $x25No: x25No )  //  match on int x25No
    $elem: ElemType( $prio: x25No == $x25No )
then
    retract($token);
end

All versions 5.[2345].0 crash. Using "0 - $prio" is a workaround.

Exception in thread "main" java.lang.NullPointerException
	at org.drools.base.mvel.MVELSalienceExpression.getValue(MVELSalienceExpression.java:93)
	at org.drools.common.DefaultAgenda.createActivation(DefaultAgenda.java:579)
	at org.drools.reteoo.RuleTerminalNode.assertLeftTuple(RuleTerminalNode.java:253)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:196)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:71)
	at org.drools.reteoo.JoinNode.propagateFromLeft(JoinNode.java:107)
	at org.drools.reteoo.JoinNode.assertLeftTuple(JoinNode.java:95)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:196)
	at org.drools.reteoo.SingleLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:145)
	at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:154)
	at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:59)
	at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
	at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:847)
	at org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:269)
	at geninq.Main.execute(Main.java:97)
	at geninq.Main.main(Main.java:133)