bug#74658: Remove the Mail-Followup-To header when empty

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 74658@debbugs.gnu.org
> From: Robert Pluim <rpluim@gmail.com>
> Date: Tue, 03 Dec 2024 15:02:58 +0100
> 
> >>>>> On Tue, 03 Dec 2024 00:17:10 +0100, Tomas Volf <~@wolfsden.cz> said:
> 
>     Tomas> Tags: patch
>     Tomas> According to the info manual (message)Mailing Lists, the
>     Tomas> Mail-Followup-To header should be removed when it is empty:
> 
>     >> If there is one, it is left alone.  (Except if it’s empty; in that
>     >> case, the field is removed and is not replaced with an automatically
>     >> generated one.  This lets you disable MFT generation on a per-message
>     >> basis.)
> 
>     Tomas> While the code attempted to do that, the call to `message-remove-header'
>     Tomas> passed wrong arguments.  Since the IS-REGEXP argument was not passed,
>     Tomas> the HEADER was considered a full header name (if I read the code right)
>     Tomas> and therefore failed to match (since the code passed in a regexp instead
>     Tomas> of a fixed string).
> 
>     Tomas> The fix is simple, remove the leading ^ and trailing :.
> 
> Yep. I can apply this to master. Maintainers, is adding
> Copyright-paperwork-exempt: yes enough here? Or do we need a copyright
> assignment from Tomas?

"Copyright-paperwork-exempt: yes" is enough.

Thanks.