The change in commit edc0d628 was flawed. The old logic covered
every case but one: having reached the end of 'buf' but 'column'
still having overshot the screen width. Now cover this latter
case too.
This fixes https://savannah.gnu.org/bugs/?55638 properly,
allowing the next commit to fix another buglet.
Condensed-by: Benno Schulenberg <bensberg@telfort.nl>
40a74e46e6