DROOLS-5786 solved the NPE but the second accumulate (in AccumulateTest.testDoubleAccumulateNPE()) produces a wrong result (= 0 instead of 2). 2 points to be fixed:

1. RuleNetworkEvaluator.doUpdatesReorderLeftMemory() causes wrong LeftTupleMemory size when calling TupleList.remove() for a tuple which doesn't exist in the list. (When removed, size becomes -1. Then added, size becomes 0. so the leftTuple is not evaluated in doRightInserts() : https://github.com/kiegroup/drools/blob/master/drools-core/src/main/java/org/drools/core/phreak/PhreakAccumulateNode.java#L215 )

2. Creating AccumulateContext right before evaluateResultConstraints() is too late. It is used by addMatch() so it needs to be created earlier (e.g. in doLeftUpdates())