2000-01-05  Garry R. Osgood <gosgood@idt.net>
*app/undo.c: GimpChannel->bounds_known field on the
image Selection Mask channel was never invalidated when restored
via undo_pop_channel_mod(). Caused PixelRegion iterators calculating
new selection boundaries to use cached image dimensions, thereby
trying to access tiles non-existent in the scaled-down image.
Closes #4840.