util: Quit early once we've found and removed a later

This prevents an invalid read and also improves performance slightly.

https://bugzilla.gnome.org/show_bug.cgi?id=672374

src/core/util.c

@@ -921,6 +921,7 @@ meta_later_remove (guint later_id)
            * repaint func run and get removed
            */
           destroy_later (later);
+          return;
         }
     }
 }