Return NULL instead of FALSE in g_return_val_if_fail in a

Return NULL instead of FALSE in g_return_val_if_fail in a

2006-03-31  Behdad Esfahbod  <behdad@gnome.org>

        * gtk/gtkfilesystem.c (gtk_file_system_get_bookmark_label):
        * gtk/gtklinkbutton.c (gtk_link_button_new_with_label): Return NULL
        instead of FALSE in g_return_val_if_fail in a pointer-returning
        function. (#336764, Morten Welinder)