ARIES-519 Stop calling update when we are not tracking a service, and…

… don't have a replacement either.

git-svn-id: https://svn.apache.org/repos/asf/incubator/aries/trunk/util@1051431 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/aries/util/SingleServiceTracker.java

@@ -104,7 +104,9 @@ private void findMatchingReference(ServiceReference original) {
           ctx.ungetService(ref);
         }
       }
-    } 
+    } else if (original == null){
+      clear = false;
+    }
 
     if (clear) {
       update(original, null, null);