bug#58312: Improve “Invalid face attribute” error message

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Wed, 10 Jan 2024 02:50:46 -0800
> Cc: Felix Dietrich <felix.dietrich@sperrhaken.name>, 58312@debbugs.gnu.org, 
> eliz@gnu.org, 
>       Po Lu <luangruo@yahoo.com>
> 
> Lars Ingebrigtsen <larsi@gnus.org> writes:
> 
> > Felix Dietrich <felix.dietrich@sperrhaken.name> writes:
> >
> >> Could the log message “Invalid face attribute” created by
> >> “xfaces.c:merge_face_ref” be extended to also include the buffer or
> >> other identifying information about its origin?
> >
> > Perhaps include the window name?  That would be less ambiguous than the
> > buffer name.
> 
> That makes sense to me.  Eli or Po Lu, WDYT about this change?

Patches welcome, but please take into account the fact that the window
is not always known there: merge_face_ref can be called with its first
argument NULL.