[gtk+/wip/csd-for-review] Fix a crash when getting header bar child properties

[Matthias Clasen <matthiasc src gnome org>]

commit c15a76c6e18b1f795915b0185ce05d51f8151b68
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Mar 10 21:59:27 2013 -0400

    Fix a crash when getting header bar child properties
    
    The find_child_link call will return NULL if the child is
    the label.

 gtk/gtkheaderbar.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index 8a13a4d..9de6175 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -905,6 +905,12 @@ gtk_header_bar_get_child_property (GtkContainer *container,
   Child *child;
 
   l = find_child_link (GTK_HEADER_BAR (container), widget);
+  if (l == NULL)
+    {
+      g_param_value_set_default (pspec, value);
+      return;
+    }
+
   child = l->data;
 
   switch (property_id)