bug#64117: 28.2; "gnus-request-set-mark: Buffer is read-only" when exiting agentized, unplugged summary buffer

[Eli Zaretskii]

> Cc: 64117@debbugs.gnu.org, Eric Abrahamsen <eric@ericabrahamsen.net>,
>  Andrew G Cohen <cohen@andy.bu.edu>
> From: Andrew Cohen <cohen@bu.edu>
> Date: Wed, 21 Jun 2023 21:52:53 +0800
> 
> Eli, this error was introduced almost 4 years ago but probably counts as
> a regression. Should we consider also fixing on 29? (Adding the use of a
> temp buffer is pretty unlikely to cause any problems).

Please show the patch, it is hard to decide without a good idea what
is about to change.

Thanks.