Race conditions in AbstractRuleBase

ReteooRuleBaseMultiThreadedTest is failing because of race conditions in AbstractRuleBase

java.lang.NullPointerException
at org.drools.common.AbstractRuleBase.lock(AbstractRuleBase.java:408)
at org.drools.common.AbstractRuleBase.removePackage(AbstractRuleBase.java:655)
at org.drools.reteoo.ReteooRuleBaseMultiThreadedTest$PackageModifier.doOperation(ReteooRuleBaseMultiThreadedTest.java:143)
at org.drools.reteoo.ReteooRuleBaseMultiThreadedTest$BlockedThread.run(ReteooRuleBaseMultiThreadedTest.java:121)

junit.framework.AssertionFailedError: Exception in modifier thread expected:<false> but was:<true>
at org.drools.reteoo.ReteooRuleBaseMultiThreadedTest.testNewSessionWhileModifyingRuleBase(ReteooRuleBaseMultiThreadedTest.java:80)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:40)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)