bug#47244: 28.0.50; SIGSEGV in long-runnning Emacs

[Eli Zaretskii]

> From: Michael Welsh Duggan <mwd@cert.org>
> Cc: Michael Welsh Duggan <mwd@md5i.com>,
>         "schwab@linux-m68k.org"
>  <schwab@linux-m68k.org>,
>         "47244@debbugs.gnu.org" <47244@debbugs.gnu.org>
> Date: Fri, 19 Mar 2021 10:21:18 -0400
> 
> Lisp Backtrace:
> "kill-buffer" (0xfffeca60)
> 0x56e58d70 PVEC_COMPILED
> "substitute-command-keys" (0xfffed728)
> "redisplay_internal (C function)" (0x0)

Thanks.  This case isn't interesting, because this is a temporary
buffer we don't display.  So I guess we need to augment the breakpoint
condition:

  break buffer.c:1840 if redisplaying_p != 0 && b->window_count > 0