clutter: Fix build with --enable-debug

Message was poking stage_x11, which doesn't exist in this context.
Just print the Window that is receiving the event, the event will be
emitted into the only existing stage anyway.

clutter/clutter/x11/clutter-device-manager-xi2.c

@@ -1160,7 +1160,7 @@ translate_pad_event (ClutterEvent       *event,
                 event->any.type == CLUTTER_PAD_RING
                 ? "pad ring  "
                 : "pad strip",
-                (unsigned int) stage_x11->xwin,
+                (unsigned int) xev->event,
                 device->id,
                 device->device_name,
                 event->any.time, value);