fullscreen-shell: avoid access to freed data

Remove the output transform from the view transform list when its
surface is destroyed. The surface destruction also triggers the
freeing of its views, so the next access to the output transform link
could crash.

Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

fullscreen-shell/fullscreen-shell.c

@@ -293,6 +293,8 @@ surface_destroyed(struct wl_listener *listener, void *data)
 					       surface_destroyed);
 	fsout->surface = NULL;
 	fsout->view = NULL;
+	wl_list_remove(&fsout->transform.link);
+	wl_list_init(&fsout->transform.link);
 }
 
 static void