Fixing a Usage leak in broker when subscribing to a topic using selector: AMQ-1889

git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@686217 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/broker/region/Topic.java

@@ -570,13 +570,15 @@ public class Topic  extends BaseDestination  implements Task{
                     return;
                 }
             }
+            
             MessageEvaluationContext msgContext = context.getMessageEvaluationContext();
             msgContext.setDestination(destination);
             msgContext.setMessageReference(message);
-
             if (!dispatchPolicy.dispatch(message, msgContext, consumers)) {
                 onMessageWithNoConsumers(context, message);
             }
+            msgContext.clear();
+            
         } finally {
             dispatchValve.decrement();
         }