[gtk+] grid: Add missing guard to gtk_grid_get_child_at()

[Bastian Winkler <bwinkler src gnome org>]

commit 4fee1aa22b44d1113a430e8f07159730f20be98a
Author: Bastian Winkler <buz netbuz org>
Date:   Sun Jun 3 01:40:41 2012 +0200

    grid: Add missing guard to gtk_grid_get_child_at()
    
    Add missing guard to make sure it's called with a GtkGrid argument.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=677363

 gtk/gtkgrid.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkgrid.c b/gtk/gtkgrid.c
index f8a281e..cbc3c34 100644
--- a/gtk/gtkgrid.c
+++ b/gtk/gtkgrid.c
@@ -1603,10 +1603,14 @@ gtk_grid_get_child_at (GtkGrid *grid,
                        gint     left,
                        gint     top)
 {
-  GtkGridPrivate *priv = grid->priv;
+  GtkGridPrivate *priv;
   GtkGridChild *child;
   GList *list;
 
+  g_return_val_if_fail (GTK_IS_GRID (grid), NULL);
+
+  priv = grid->priv;
+
   for (list = priv->children; list; list = list->next)
     {
       child = list->data;