bug#23871: 25.1.50; Undo unexpectedly leads to blank buffer

[Eli Zaretskii]

> Date: Thu, 30 Jun 2016 21:21:31 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 23871@debbugs.gnu.org
> 
> > 2) C-x = immediately after undo confirms this, saying:
> > 
> >    point=323 of 322 (EOB) column=0
> > 
> >    While point before undo is point 281 of 322.
> 
> I'm not sure this is not the expected behavior.  This means the blank
> buffer you see is just the last empty line with EOB.  The Emacs
> display engine should not normally allow that, it should show the last
> line before EOB.

The above meant to say that it could be the expected undo behavior,
but if so, the display engine probably has some issue in this
situation.