ClutterStage: Don't add empty actors to the stage clip

Currently, if an actor with an empty paint volume is queued for redraw, it
will union in the box +0+0x1x1 to the stage clip bounds - avoid that
by special casing empty paint volumes.

https://bugzilla.gnome.org/show_bug.cgi?id=719747

clutter/clutter-stage.c

@@ -1312,6 +1312,9 @@ clutter_stage_real_queue_redraw (ClutterActor *actor,
       return;
     }
 
+  if (redraw_clip->is_empty)
+    return;
+
   _clutter_paint_volume_get_stage_paint_box (redraw_clip,
                                              stage,
                                              &bounding_box);