[gtk+] gdk: don't segfault on beep with offscreen window

[Matthias Clasen <matthiasc src gnome org>]

commit b44afa1d486e6f1f017e0d149634e781c3706669
Author: Christian Hergert <christian hergert me>
Date:   Wed Apr 22 16:35:29 2015 -0700

    gdk: don't segfault on beep with offscreen window
    
    https://bugzilla.gnome.org/show_bug.cgi?id=748341

 gdk/gdkoffscreenwindow.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkoffscreenwindow.c b/gdk/gdkoffscreenwindow.c
index f9e8182..614e3f0 100644
--- a/gdk/gdkoffscreenwindow.c
+++ b/gdk/gdkoffscreenwindow.c
@@ -669,6 +669,12 @@ gdk_offscreen_window_set_opacity (GdkWindow *window, gdouble opacity)
 {
 }
 
+static gboolean
+gdk_offscreen_window_beep (GdkWindow *window)
+{
+  return FALSE;
+}
+
 static void
 gdk_offscreen_window_class_init (GdkOffscreenWindowClass *klass)
 {
@@ -701,7 +707,7 @@ gdk_offscreen_window_class_init (GdkOffscreenWindowClass *klass)
   impl_class->destroy_foreign = NULL;
   impl_class->get_shape = NULL;
   impl_class->get_input_shape = NULL;
-  impl_class->beep = NULL;
+  impl_class->beep = gdk_offscreen_window_beep;
 
   impl_class->focus = NULL;
   impl_class->set_type_hint = NULL;