[gtk+] Ensure a variable is initialized

[Matthias Clasen <matthiasc src gnome org>]

commit 5a446284b7e4710e11daf9cf5e412e5fbf18e4b9
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jun 13 17:49:20 2015 -0400

    Ensure a variable is initialized
    
    clang complained about transient_for being used uninitialized.

 gdk/wayland/gdkwindow-wayland.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index fded03a..4c448d7 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -1174,7 +1174,7 @@ static void
 gdk_wayland_window_map (GdkWindow *window)
 {
   GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
-  GdkWindow *transient_for;
+  GdkWindow *transient_for = NULL;
 
   if (!should_be_mapped (window))
     return;