OF-270: Patch by LG - first delete any pending presences, before adding a new...

OF-270: Patch by LG - first delete any pending presences, before adding a new one. Should be crude/effective.

git-svn-id: http://svn.igniterealtime.org/svn/repos/openfire/trunk@12956 b35dd754-fafc-0310-a699-88a17e54d16e

src/java/org/jivesoftware/openfire/spi/PresenceManagerImpl.java

@@ -273,7 +273,7 @@ public class PresenceManagerImpl extends BasicModule implements PresenceManager,
             }
             lastActivityCache.put(username, offlinePresenceDate.getTime());
 
-            // delete existing offline presence
+            // delete existing offline presence (if any)
             deleteOfflinePresenceFromDB(username);
             
             // Insert data into the database.