[mutter] wayland: Avoid MetaWindow call on non window-backed surfaces

[Carlos Garnacho <carlosg src gnome org>]

commit 7c5989c978ed6ca0fc0e86b5642ae122bef0a814
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Oct 20 18:41:22 2014 +0200

    wayland: Avoid MetaWindow call on non window-backed surfaces
    
    Crossing events may also be gotten on subsurfaces.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=738890

 src/wayland/meta-wayland-pointer.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/src/wayland/meta-wayland-pointer.c b/src/wayland/meta-wayland-pointer.c
index 9f6c264..b7a36f5 100644
--- a/src/wayland/meta-wayland-pointer.c
+++ b/src/wayland/meta-wayland-pointer.c
@@ -518,10 +518,11 @@ meta_wayland_pointer_set_focus (MetaWaylandPointer *pointer,
 
       clutter_input_device_get_coords (pointer->device, NULL, &pos);
 
-      meta_window_handle_enter (pointer->focus_surface->window,
-                                /* XXX -- can we reliably get a timestamp for setting focus? */
-                                clutter_get_current_event_time (),
-                                pos.x, pos.y);
+      if (pointer->focus_surface->window)
+        meta_window_handle_enter (pointer->focus_surface->window,
+                                  /* XXX -- can we reliably get a timestamp for setting focus? */
+                                  clutter_get_current_event_time (),
+                                  pos.x, pos.y);
 
       move_resources_for_client (&pointer->focus_resource_list,
                                  &pointer->resource_list,