bug#35784: emacs 26 crash

[Eli Zaretskii]

> Cc: 35784@debbugs.gnu.org, marc@bloodnok.com
> From: martin rudalics <rudalics@gmx.at>
> Date: Sat, 18 May 2019 19:30:50 +0200
> 
>  > This seems to imply that we are trying to update a non-leaf window,
>  > something that should never happen.  There's no Lisp-level backtrace,
>  > so it's hard to tell what Lisp called force-window-update, and how the
>  > window in question became non-leaf, but maybe some crazy Lisp hook
>  > switched windows behind redisplay's back or something.
> 
> I'd rather guess that this is the result of 'kill-buffer' called from
> 'delete-frame-functions' or 'delete-frame' called from
> 'kill-buffer-hook'.

kill-buffer is supposed to replace the killed buffer with another in
all windows, so we shouldn't end up with a window's buffer being nil.
But I'm louse at guessing causes for problems just by looking at them,
so you may be right.