bug#52461: spontaneous crash with portable dumper

[Eli Zaretskii]

> Date: Tue, 14 Dec 2021 17:04:48 +0900
> From: YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp>
> Cc: Pip Cet <pipcet@gmail.com>,
>       52461@debbugs.gnu.org
> 
> I directly inserted the memset line just after the xpalloc call in
> charset.c, and dumped 10 times.  No crash occured.
> 
> I also tried the change below, and it seems to work, too.

Thanks.  I think I prefer the second variant.

Do you think we need more testing of this, since the problem was
intermittent?