2004-10-28  Sven Neumann  <sven@gimp.org>

	* app/actions/layers-actions.c (layers_actions_update): do not set
	the "layers-mask-add" action insensitive if there's no alpha channel.

	* app/actions/layers-commands.c (layers_add_mask_response): add an
	alpha channel if there isn't one already. Fixes bug #156676.