bug#56773: 29.0.50; (readablep UNREADABLE) causes strange things

[Michael Heerdegen]

Hello,

emacs -Q:

(progn (readablep (current-window-configuration))
       (current-buffer))
==> #<buffer  prin1>

After evaluating such a `readablep' call, weird things can happen
because of this buffer being current.  I tried to actually display that
buffer and the window I got looked quite funny, one second later Emacs
had crashed.

TIA,

Michael.


In GNU Emacs 29.0.50 (build 31, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, 
cairo version 1.16.0)
 of 2022-07-26 built on drachen
Repository revision: c455023f93f5073e7032a2097821e23eafa6f1aa
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)