2004-10-13  Sven Neumann  <sven@gimp.org>

	* app/core/gimpimagefile.c (gimp_imagefile_create_thumbnail): ref
	the imagefile while creating the thumbnail.

	* app/core/gimpimagefile.[ch]
	* app/widgets/gimpthumbbox.c (gimp_thumb_box_auto_thumbnail): moved
	the tricky part about thumbnail creation into the new function
	gimp_imagefile_create_thumbnail_weak().