[gtk+] wayland: Add NULL warning check to _gdk_wayland_window_set_device_grabbed

[Rob Bradford <rbradford src gnome org>]

commit ff2acecac62bd6738511de480669f159a5ffd45e
Author: Rob Bradford <rob linux intel com>
Date:   Mon Mar 5 19:41:11 2012 +0000

    wayland: Add NULL warning check to _gdk_wayland_window_set_device_grabbed

 gdk/wayland/gdkwindow-wayland.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 24a2e93..2f6740b 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -1512,7 +1512,11 @@ _gdk_wayland_window_set_device_grabbed (GdkWindow              *window,
                                         struct wl_input_device *input_device,
                                         guint32                 time_)
 {
-  GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
+  GdkWindowImplWayland *impl;
+
+  g_return_if_fail (window != NULL);
+
+  impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
 
   impl->grab_input_device = input_device;
   impl->grab_time = time_;