[gtk+] Fix crash

[Behdad Esfahbod <behdad src gnome org>]

commit 024c11dd66dfda5efb110f55ecec93801f21c0ed
Author: Behdad Esfahbod <behdad behdad org>
Date:   Thu May 22 15:52:01 2014 -0400

    Fix crash

 gtk/gtkcssenumvalue.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcssenumvalue.c b/gtk/gtkcssenumvalue.c
index a8c807b..08ae60a 100644
--- a/gtk/gtkcssenumvalue.c
+++ b/gtk/gtkcssenumvalue.c
@@ -485,6 +485,7 @@ _gtk_css_area_value_try_parse (GtkCssParser *parser)
 GtkCssArea
 _gtk_css_area_value_get (const GtkCssValue *value)
 {
+  g_return_val_if_fail (value != NULL, GTK_CSS_AREA_BORDER_BOX);
   g_return_val_if_fail (value->class == &GTK_CSS_VALUE_AREA, GTK_CSS_AREA_BORDER_BOX);
 
   return value->value;