[gtk+] Don't clear data on a NULL screen

[Matthias Clasen <matthiasc src gnome org>]

commit 97caad1fece17320db481ebf1933ad306c68fe3f
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri May 3 20:03:12 2013 -0400

    Don't clear data on a NULL screen
    
    This makes GtkSettings survive the object finalize test.

 gtk/gtksettings.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtksettings.c b/gtk/gtksettings.c
index 0288c61..12d2aa1 100644
--- a/gtk/gtksettings.c
+++ b/gtk/gtksettings.c
@@ -2717,7 +2717,7 @@ settings_update_provider (GdkScreen       *screen,
                           GtkCssProvider **old,
                           GtkCssProvider  *new)
 {
-  if (*old != new)
+  if (screen != NULL && *old != new)
     {
       if (*old)
         {