[CORE][QUEUE] Error checking and type declaration on handling notice queue events

Patch submitted by XRevan86

lib/queuehandler.php

@@ -46,7 +46,7 @@ class QueueHandler
      * @param mixed $object
      * @return boolean true on success, false on failure
      */
-    function handle($object)
+    function handle($object): bool
     {
         return true;
     }