Check that index is not bigger than level array length also when depth is

Check that index is not bigger than level array length also when depth is

2003-12-17  Marco Pesenti Gritti  <marco@gnome.org>

        * gtk/gtktreemodelsort.c: (gtk_tree_model_sort_get_iter):

        Check that index is not bigger than level array length
        also when depth is 1. Now get_iter_first correctly return
        FALSE when the model is empty (#129411).