bug#42943: 28.0.50; Emacsclient crashes in ftcrfont_glyph_extents

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: contovob@tcd.ie,  larsi@gnus.org,  42943@debbugs.gnu.org
> Date: Sat, 24 Oct 2020 17:41:36 +0200
> 
>     >> OK, so when we are about to release a font, we need to go over all the
>     >> LGSTRING objects in gstring_hash_table, and remove from that cache
>     >> every LGSTRING whose LGSTRING_FONT object holds the font we are about
>     >> to release.
> 
>     Eli> Here, does the below give good results?
> 
> I should really hit 'g' in Gnus before writing patches :-)
> 
> That fixes it as well.

OK, thanks.  (I think clearing the entire cache of gstrings is too
radical: we don't necessarily remove all the fonts from all the
frames.)

Now the important question: should we install this on master or on the
release branch?  I believe the problem is not limited to 28.0.50, is
it?  OTOH, is this safe enough to install on emacs-27?