[gtk+] win32: Don't dereference keyboard_grab if it is NULL

[Alexander Larsson <alexl src gnome org>]

commit 0d94b974b3e7564b130fe5960a636bae9fa08a1d
Author: Alexander Larsson <alexl redhat com>
Date:   Mon Nov 21 14:37:57 2011 +0100

    win32: Don't dereference keyboard_grab if it is NULL
    
    This fixes a crash in e.g. testdnd

 gdk/win32/gdkevents-win32.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index 16d8195..83adae6 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -2730,7 +2730,8 @@ gdk_event_translate (MSG  *msg,
 		gdk_pointer_ungrab (msg->time);
 	    }
 
-	  if (keyboard_grab->window == window)
+	  if (keyboard_grab != NULL &&
+	      keyboard_grab->window == window)
 	    gdk_keyboard_ungrab (msg->time);
 	}