and call gimp_image_convert_indexed() in image-commands.c where it
belongs. Also remember the default values there, they will to to
GimpDialogConfig next.
They are unreliable because every type checking cast discards them,
they are useless anyway, visual clutter, added inconsistently, and
generally suck. Wanted to do this a long time ago, it was a bad idea
in the first place.