java.lang.NullPointerException
	at org.drools.core.reteoo.builder.WindowReferenceBuilder.build(WindowReferenceBuilder.java:40)
	at org.drools.core.reteoo.builder.PatternBuilder.attachPattern(PatternBuilder.java:117)
	at org.drools.core.reteoo.builder.PatternBuilder.build(PatternBuilder.java:78)
	at org.drools.core.reteoo.builder.AccumulateBuilder.build(AccumulateBuilder.java:67)
	at org.drools.core.reteoo.builder.PatternBuilder.attachPattern(PatternBuilder.java:117)
	at org.drools.core.reteoo.builder.PatternBuilder.build(PatternBuilder.java:78)
	at org.drools.core.reteoo.builder.GroupElementBuilder$AndBuilder.build(GroupElementBuilder.java:108)
	at org.drools.core.reteoo.builder.GroupElementBuilder.build(GroupElementBuilder.java:68)
	at org.drools.core.reteoo.builder.ReteooRuleBuilder.addSubRule(ReteooRuleBuilder.java:164)
	at org.drools.core.reteoo.builder.ReteooRuleBuilder.addRule(ReteooRuleBuilder.java:136)
	at org.drools.core.reteoo.ReteooBuilder.addRule(ReteooBuilder.java:102)
	at org.drools.core.impl.KnowledgeBaseImpl.addRule(KnowledgeBaseImpl.java:1521)
	at org.drools.core.impl.KnowledgeBaseImpl.addRule(KnowledgeBaseImpl.java:1501)
	at org.drools.core.impl.KnowledgeBaseImpl.internalAddPackages(KnowledgeBaseImpl.java:868)
	at org.drools.core.impl.KnowledgeBaseImpl.addPackages(KnowledgeBaseImpl.java:723)
	at org.drools.core.impl.KnowledgeBaseImpl.addKnowledgePackages(KnowledgeBaseImpl.java:277)
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.createKieBase(KieContainerImpl.java:493)
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieBase(KieContainerImpl.java:452)
	at org.drools.compiler.kie.builder.impl.KieContainerImpl.newKieBase(KieContainerImpl.java:447)
	at org.kie.internal.utils.KieHelper.build(KieHelper.java:77)
	at org.drools.compiler.integrationtests.LengthSlidingWindowTest.checkPrice(LengthSlidingWindowTest.java:96)
	at org.drools.compiler.integrationtests.LengthSlidingWindowTest.testSlidingWindowWithDeclaration(LengthSlidingWindowTest.java:89)