Possible method call on null object in QueueImpl class

public void postAcknowledge(final MessageReference ref) {code:java}

{code:java}
      boolean durableRef = message != null && message.isDurable() && queue.durable;         \\line 2461

      try {
         message.decrementRefCount();                                                       \\line 2464
      }
      catch (Exception e) {
         ActiveMQServerLogger.LOGGER.errorDecrementingRefCount(e);
      }