[gtk+] sidebar: Fix gcc warning

[Benjamin Otte <otte src gnome org>]

commit 93aeb63f0c1d45405b5aea1d3dfe2d5d339a183b
Author: Benjamin Otte <otte redhat com>
Date:   Thu Oct 2 03:00:39 2014 +0200

    sidebar: Fix gcc warning

 gtk/gtksidebar.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtksidebar.c b/gtk/gtksidebar.c
index 437f692..7e9fe6f 100644
--- a/gtk/gtksidebar.c
+++ b/gtk/gtksidebar.c
@@ -512,7 +512,7 @@ gtk_sidebar_get_stack (GtkSidebar *sidebar)
 {
   GtkSidebarPrivate *priv;
 
-  g_return_if_fail (GTK_IS_SIDEBAR (sidebar));
+  g_return_val_if_fail (GTK_IS_SIDEBAR (sidebar), NULL);
 
   priv = gtk_sidebar_get_instance_private (sidebar);