[gtk+] Fix compiler warning.

[Carlos Garnacho <carlosg src gnome org>]

commit e426f76e5797b6a2cc9e26d76bc35e52f687aa8f
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Jan 10 23:48:22 2011 +0100

    Fix compiler warning.

 gtk/gtkwidget.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 16fd511..d1eee5b 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -4243,9 +4243,9 @@ get_widget_windows (GtkWidget *widget)
 
   for (l = window_list; l; l = l->next)
     {
-      GtkWidget *window_widget;
+      GtkWidget *window_widget = NULL;
 
-      gdk_window_get_user_data (l->data, (gpointer *) window_widget);
+      gdk_window_get_user_data (l->data, (gpointer *) &window_widget);
 
       if (widget != window_widget)
         continue;