[gtk+] GtkHeaderBar: Fix a corner-case in child properties

[Matthias Clasen <matthiasc src gnome org>]

commit 287319564450211a88e313d99eb3381016ae8074
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Nov 2 17:46:35 2014 -0500

    GtkHeaderBar: Fix a corner-case in child properties
    
    The child property setting must be prepared to deal with any
    child property for any child, even if it doesn't make sense,
    like the pack-type for the custom title. This is happening
    in glade when undoing a change in the custom-title property.

 gtk/gtkheaderbar.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index 2dd8dee..540a461 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -1650,6 +1650,9 @@ gtk_header_bar_set_child_property (GtkContainer *container,
   Child *child;
 
   l = find_child_link (bar, widget);
+  if (l == NULL)
+    return;
+
   child = l->data;
 
   switch (property_id)