NullPointerException in LHS constraint in BRMS

Issue

• I get NullPointerException while runnintg rules. The error message doesn't give much idea.

[Error: null pointer: trailer.name]
[Near : {... trailer.name == "John" ....}]
             ^
[Line: 1, Column: 1]
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:427)
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:140)
    at org.mvel2.ast.ASTNode.optimize(ASTNode.java:159)
    at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:115)
    at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:114)
    at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:42)
    at org.mvel2.MVEL.executeExpression(MVEL.java:930)
    at org.drools.core.util.MVELSafeHelper$RawMVELEvaluator.executeExpression(MVELSafeHelper.java:481)
    at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:77)
    at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:62)
    at org.drools.core.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:217)
    at org.drools.core.rule.constraint.MvelConstraint.isAllowed(MvelConstraint.java:174)
    at org.drools.core.reteoo.AlphaNode.assertObject(AlphaNode.java:134)
    at org.drools.core.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:60)
    at org.drools.core.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:288)
    at org.drools.core.reteoo.EntryPointNode.assertObject(EntryPointNode.java:260)
    at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:368)
    at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:287)
    at org.drools.core.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1143)
    at org.drools.core.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1087)
    at org.drools.core.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:308)
    at com.sample.DroolsTest.main(DroolsTest.java:28)
Caused by: java.lang.NullPointerException
    at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:393)
    ... 21 more