Check args for NULL. (gtk_selection_default_handler): Replace manual list

Check args for NULL. (gtk_selection_default_handler): Replace manual list

Thu Jan 21 17:13:12 1999  Jeff Garzik  <jgarzik@pobox.com>

        * gtk/gtkselection.c:
        (gtk_selection_property_notify): Check args for NULL.
        (gtk_selection_default_handler):
        Replace manual list count with call to g_list_length.
        Remove signedness of temp var 'count' to agree with usage.
        Slight spacing adjustment for readability.

        * gtk/gtkbox.c, gtk/gtklayout.c, gtk/gtkselection.c:
        Init a few ptrs to NULL, to quiet warnings.