set radio_menu_item->group to NULL after removing it from the list, as it

set radio_menu_item->group to NULL after removing it from the list, as it

2001-09-21  Matt Wilson  <msw@redhat.com>

	* gtk/gtkradiomenuitem.c (gtk_radio_menu_item_destroy): set
	radio_menu_item->group to NULL after removing it from the list, as
	it is no longer in the group. (#60869)

	* gtk/gtkradiobutton.c (gtk_radio_button_destroy): likewise