bug#41445: 26.3; Query-replace triggers "match data clobbered by..."

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Fri, 22 May 2020 12:46:03 +0200
> Cc: 41445@debbugs.gnu.org
> 
> Thank you! Clearly nobody expects normalisation functions to clobber match 
> data.

Is that the right place to save-match-data, though?  Should we perhaps
do that where utf-8-hfs file names are encoded?

Thanks.