bug#28997: 27.0.50; Error in async shell-command process filter

[Basil L. Contovounesios]

Eli Zaretskii <eliz@gnu.org> writes:

> We try to fix bugs on the release branch, especially bugs in changes
> introduced since the last release.

This bug was introduced in 85512e7521 "Allow async command
output buffer to be shown only on output", which was first
released with the current pretest 26.0.90.

-- 
Basil