[gnome-control-center] universal-access: Don't crash when metacity isn't installed

[Bastien Nocera <hadess src gnome org>]

commit b8b3df03fcaf1f8e438d6c94f081f40b165d1e72
Author: Bastien Nocera <hadess hadess net>
Date:   Fri Aug 26 19:20:52 2011 +0100

    universal-access: Don't crash when metacity isn't installed

 panels/universal-access/cc-ua-panel.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/panels/universal-access/cc-ua-panel.c b/panels/universal-access/cc-ua-panel.c
index 2a0f093..c125ba4 100644
--- a/panels/universal-access/cc-ua-panel.c
+++ b/panels/universal-access/cc-ua-panel.c
@@ -551,7 +551,11 @@ visual_bell_type_notify_cb (GConfClient *client,
                             CcUaPanel   *panel)
 {
   GtkWidget *widget;
-  const gchar *value = gconf_value_get_string (entry->value);
+  const gchar *value;
+
+  g_return_if_fail (entry != NULL);
+
+  value = gconf_value_get_string (entry->value);
 
   if (!strcmp ("frame_flash", value))
     widget = WID (panel->priv->builder, "hearing_flash_window_title_button");