[gtk+/native-layout] Handle out-of-bounds parameters in gtk_assistant_get_nth_page

[Tristan Van Berkom <tvb src gnome org>]

commit 624ac853bac75ee5de03b272eba7b46ac3808e3a
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Feb 23 11:23:10 2010 -0500

    Handle out-of-bounds parameters in gtk_assistant_get_nth_page
    
    Better do what the docs say...fix by Tadej Borovšak, bug 610141.

 gtk/gtkassistant.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkassistant.c b/gtk/gtkassistant.c
index daec0cf..5fd6d83 100644
--- a/gtk/gtkassistant.c
+++ b/gtk/gtkassistant.c
@@ -1615,10 +1615,14 @@ gtk_assistant_get_nth_page (GtkAssistant *assistant,
   GList *elem;
 
   g_return_val_if_fail (GTK_IS_ASSISTANT (assistant), NULL);
+  g_return_val_if_fail (page_num >= -1, NULL);
 
   priv = assistant->priv;
 
-  elem = g_list_nth (priv->pages, page_num);
+  if (page_num == -1)
+    elem = g_list_last (priv->pages);
+  else
+    elem = g_list_nth (priv->pages, page_num);
 
   if (!elem)
     return NULL;