[gtksourceview/wip/fix-warnings] UndoManagerDefault: fix warning

[Sébastien Wilmet <swilmet src gnome org>]

commit c5fcb5381621c189016f0c5b6a40d1b4ed8796e8
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Aug 9 16:59:39 2015 +0200

    UndoManagerDefault: fix warning

 gtksourceview/gtksourceundomanagerdefault.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtksourceview/gtksourceundomanagerdefault.c b/gtksourceview/gtksourceundomanagerdefault.c
index 379579a..3a05906 100644
--- a/gtksourceview/gtksourceundomanagerdefault.c
+++ b/gtksourceview/gtksourceundomanagerdefault.c
@@ -372,7 +372,9 @@ check_history_size (GtkSourceUndoManagerDefault *manager)
                return;
        }
 
-       while (manager->priv->action_groups->length > manager->priv->max_undo_levels)
+       g_return_if_fail (manager->priv->max_undo_levels > 0);
+
+       while (manager->priv->action_groups->length > (guint)manager->priv->max_undo_levels)
        {
                /* Strip redo action groups first. */
                if (manager->priv->location != NULL)