Race condition causing jitting error

When there is a rule that retracts a fact while a MvelConstraint.ConditionJitter task runs, then sometimes the jitting task fails with this error...

java.lang.NullPointerException
at org.drools.base.defaultpkg.Person13506221$getField10.getValue(Unknown Source)
at org.drools.base.ClassFieldReader.getValue(ClassFieldReader.java:87)
at org.drools.rule.Declaration.getValue(Declaration.java:233)
at org.drools.base.mvel.MVELCompilationUnit.updateFactory(MVELCompilationUnit.java:344)
at org.drools.base.mvel.MVELCompilationUnit.updateFactory(MVELCompilationUnit.java:289)
at org.drools.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:62)
at org.drools.rule.constraint.MvelConditionEvaluator.ensureBranchEvaluation(MvelConditionEvaluator.java:120)
at org.drools.rule.constraint.MvelConditionEvaluator.ensureCompleteEvaluation(MvelConditionEvaluator.java:105)
at org.drools.rule.constraint.MvelConditionEvaluator.ensureCompleteEvaluation(MvelConditionEvaluator.java:93)
at org.drools.rule.constraint.MvelConditionEvaluator.getAnalyzedCondition(MvelConditionEvaluator.java:85)
at org.drools.rule.constraint.MvelConstraint.executeJitting(MvelConstraint.java:284)
at org.drools.rule.constraint.MvelConstraint.access$200(MvelConstraint.java:54)
at org.drools.rule.constraint.MvelConstraint$ConditionJitter.run(MvelConstraint.java:263)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)