rule "globalRequiredPredecessorAfterMe"
    when 
        $rpAll: Set(size>1) from accumulate (
        	Customer(Domicile != null, $rpAfterMe: requiredPredecessorsAfterMe);
        		collectSet($rpAfterMe)
        	)
    then
        scoreHolder.addMediumConstraintMatch(kcontext, - $rpAll.size()-1);
  end

Exception in thread "main" java.lang.RuntimeException: java.lang.NullPointerException
	at org.drools.core.rule.SingleAccumulate.reverse(SingleAccumulate.java:124)
	at org.drools.core.phreak.PhreakAccumulateNode.removeMatch(PhreakAccumulateNode.java:796)
	at org.drools.core.phreak.PhreakAccumulateNode.doRightUpdatesProcessChildren(PhreakAccumulateNode.java:517)
	at org.drools.core.phreak.PhreakAccumulateNode.doRightUpdates(PhreakAccumulateNode.java:450)
	at org.drools.core.phreak.PhreakAccumulateNode.doNode(PhreakAccumulateNode.java:76)
	at org.drools.core.phreak.RuleNetworkEvaluator.switchOnDoBetaNode(RuleNetworkEvaluator.java:581)
	at org.drools.core.phreak.RuleNetworkEvaluator.evalBetaNode(RuleNetworkEvaluator.java:552)
	at org.drools.core.phreak.RuleNetworkEvaluator.evalNode(RuleNetworkEvaluator.java:379)
	at org.drools.core.phreak.RuleNetworkEvaluator.innerEval(RuleNetworkEvaluator.java:339)
	at org.drools.core.phreak.RuleNetworkEvaluator.outerEval(RuleNetworkEvaluator.java:175)
	at org.drools.core.phreak.RuleNetworkEvaluator.evaluateNetwork(RuleNetworkEvaluator.java:133)
	at org.drools.core.phreak.RuleExecutor.reEvaluateNetwork(RuleExecutor.java:212)
	at org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:87)
	at org.drools.core.concurrent.AbstractRuleEvaluator.internalEvaluateAndFire(AbstractRuleEvaluator.java:34)
	at org.drools.core.concurrent.SequentialRuleEvaluator.evaluateAndFire(SequentialRuleEvaluator.java:43)
	at org.drools.core.common.DefaultAgenda.fireLoop(DefaultAgenda.java:1067)
	at org.drools.core.common.DefaultAgenda.internalFireAllRules(DefaultAgenda.java:1014)
	at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1006)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.internalFireAllRules(StatefulKnowledgeSessionImpl.java:1337)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1328)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1312)
	at org.optaplanner.core.impl.score.director.drools.DroolsScoreDirector.calculateScore(DroolsScoreDirector.java:117)
	at org.optaplanner.core.impl.score.director.AbstractScoreDirector.doAndProcessMove(AbstractScoreDirector.java:187)
	at org.optaplanner.core.impl.constructionheuristic.decider.ConstructionHeuristicDecider.doMove(ConstructionHeuristicDecider.java:126)
	at org.optaplanner.core.impl.constructionheuristic.decider.ConstructionHeuristicDecider.decideNextStep(ConstructionHeuristicDecider.java:100)
	at org.optaplanner.core.impl.constructionheuristic.DefaultConstructionHeuristicPhase.solve(DefaultConstructionHeuristicPhase.java:74)
	at org.optaplanner.core.impl.solver.AbstractSolver.runPhases(AbstractSolver.java:88)
	at org.optaplanner.core.impl.solver.DefaultSolver.solve(DefaultSolver.java:191)
	at canihazafischbroetchenplz.app.TestApp.main(TestApp.java:35)
Caused by: java.lang.NullPointerException
	at org.drools.core.base.accumulators.CollectSetAccumulateFunction.reverse(CollectSetAccumulateFunction.java:118)
	at org.drools.core.base.accumulators.CollectSetAccumulateFunction.reverse(CollectSetAccumulateFunction.java:49)
	at org.drools.core.base.accumulators.JavaAccumulatorFunctionExecutor.reverse(JavaAccumulatorFunctionExecutor.java:133)
	at org.drools.core.rule.SingleAccumulate.reverse(SingleAccumulate.java:116)
	... 28 more