pass a valid bundle context to the GrowlNotificationService rather than a null object

src/net/java/sip/communicator/impl/growlnotification/GrowlNotificationActivator.java

@@ -54,7 +54,7 @@ public void start(BundleContext bc) throws Exception
                         "on JDK version " + version);
         } else {
             /* Create and start the Growl Notification service. */
-            new GrowlNotificationServiceImpl().start(bundleContext);
+            new GrowlNotificationServiceImpl().start(bc);
 
             logger.info("Growl Notification Plugin ...[Started]");
         }