An operation on a JMX iiop connector may get a NullpointerException because of a synchronization problem from the IIOP implementation: 6360330

For example, when testing our event service, we got:
    [exec] STDERR:
    [exec] java.lang.NullPointerException
    [exec] at com.sun.corba.se.impl.protocol.SharedCDRClientRequestDispatcherImpl.marshalingComplete(SharedCDRClientRequestDispatcherImpl.java:178)
    [exec] at com.sun.corba.se.impl.protocol.CorbaClientDelegateImpl.invoke(CorbaClientDelegateImpl.java:129)
    [exec] at org.omg.CORBA.portable.ObjectImpl._invoke(ObjectImpl.java:457)
    [exec] at com.sun.jmx.remote.internal.ProxyStub._invoke(Unknown Source)
    [exec] at org.omg.stub.javax.management.remote.rmi._RMIConnection_Stub.invoke(Unknown Source)
    [exec] at javax.management.remote.rmi.RMIConnector$RemoteMBeanServerConnection.invoke(RMIConnector.java:1032)
    [exec] at javax.management.MBeanServerInvocationHandler.invoke(MBeanServerInvocationHandler.java:330)
    [exec] at $Proxy1.removeListener(Unknown Source)
    [exec] at javax.management.event.EventClient.removeListener(EventClient.java:1068)
    [exec] at javax.management.event.EventClient.removeNotificationListener(EventClient.java:512)
    [exec] at AddRemoveListenerTest.test(AddRemoveListenerTest.java:205)
    [exec] at AddRemoveListenerTest.access$100(AddRemoveListenerTest.java:56)
    [exec] at AddRemoveListenerTest$Job.run(AddRemoveListenerTest.java:166)
    [exec] at java.lang.Thread.run(Thread.java:619)
    [exec] STATUS:Failed.`main' threw exception: java.lang.NullPointerException