[21.5.27] Another crash, this time in search.c, reproducible

[Stephen J. Turnbull]

Holger Schauer writes:

 > writing some posting in Gnus (message), I got another crash. This time
 > it's reproducible with the autosaved message, which I'll append as
 > well as the backtrace.

Please explain the exact operations to produce the crash, starting
with "xemacs -vanilla".  I was unable to get a crash, either by
reading the file into a buffer or by changing to message-mode and
attempting to send it (I don't have news installed on that box so it
wouldn't have gone out, anyway).