[gtksourceview] Add missing g_return_val_if_fail()

[SÃbastien Wilmet <swilmet src gnome org>]

commit 8ccf35fce112c7d763028c6d5cfbc5d8fc8e5c64
Author: SÃbastien Wilmet <swilmet gnome org>
Date:   Thu Feb 14 15:07:43 2013 +0100

    Add missing g_return_val_if_fail()

 gtksourceview/gtksourcecompletion.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gtksourceview/gtksourcecompletion.c b/gtksourceview/gtksourcecompletion.c
index f86656e..3ad3f57 100644
--- a/gtksourceview/gtksourcecompletion.c
+++ b/gtksourceview/gtksourcecompletion.c
@@ -3519,6 +3519,8 @@ gtk_source_completion_hide (GtkSourceCompletion *completion)
 GtkSourceCompletionInfo *
 gtk_source_completion_get_info_window (GtkSourceCompletion *completion)
 {
+       g_return_val_if_fail (GTK_SOURCE_IS_COMPLETION (completion), NULL);
+
        return GTK_SOURCE_COMPLETION_INFO (completion->priv->info_window);
 }