[gtk+] Don't whine about expander-style missing

[Carlos Garnacho <carlosg src gnome org>]

commit eb8a1c4e33480043fbfb0e1bf3c254f0ce784dfa
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Nov 16 07:52:27 2010 -0500

    Don't whine about expander-style missing
    
    This check was lost in the GtkStyleContext porting.

 gtk/gtkstyle.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkstyle.c b/gtk/gtkstyle.c
index ff3ba06..5a357b4 100644
--- a/gtk/gtkstyle.c
+++ b/gtk/gtkstyle.c
@@ -3187,7 +3187,9 @@ gtk_default_draw_expander (GtkStyle        *style,
       break;
     }
 
-  if (widget)
+  if (widget &&
+      gtk_widget_class_find_style_property (GTK_WIDGET_GET_CLASS (widget),
+                                            "expander-size"))
     gtk_widget_style_get (widget, "expander-size", &size, NULL);
   else
     size = 12;