bug#35784: emacs 26 crash

[martin rudalics <rudalics@gmx.at>]

 >> #2  0x000000000061849e in die (msg=0x743f3f "BUFFERP (a)",
 >> file=0x743f36 "buffer.h", line=914) at alloc.c:7406
 >> #3  0x00000000005802b3 in XBUFFER (a=0) at buffer.h:914
 >> #4  0x0000000000468bb3 in mark_window_display_accurate_1 (w=0x558e410,
 >> accurate_p=false) at xdisp.c:14754
 >>          b = 0x7ffe74b60e40
 >> #5  0x0000000000468ffd in mark_window_display_accurate
 >> (window=89711637, accurate_p=false) at xdisp.c:14811
 >>          w = 0x558e410
 >> #6  0x00000000004bbe06 in Fforce_window_update (object=89711637) at
 >> window.c:3643
 >>          w = 0x558e410
 >
 > 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'.  But at the moment I can't reproduce the bug here
any more.

martin