fix inappropriate merge during aborted throw

fix inappropriate merge during aborted throw

Fix the situation reported by Pasi where cancelling a throw via ESC at
the "which direction?" prompt resulted in "object null after merge"
panic from addinv().  I wasn't able to reproduce the panic, but I could
see the throw-nowhere stack getting merged into the quiver stack when
it shouldn't.  This fixes that.

Also a couple of formatting bits.  I wish I'd quit coming across those.