bug#30519: 26.0.91; Emacs hangs with flyspell overlay

[Eli Zaretskii]

> Cc: 30519@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 20 Feb 2018 01:47:33 +0200
> 
> On 2/19/18 6:32 PM, Eli Zaretskii wrote:
> 
> >> Emacs hangs with repeating error "Marker does not point anywhere". You
> >> can clear the hang by moving the mouse pointer.
> > 
> > Not reproducible here.  Could this be X-specific (I tried on Windows)?
> 
> I can reproduce this in emacs-26 (Ubuntu 17.10 with GTK3 here).

Thanks.

A C- and Lisp-level backtrace from the place which signals that error
would be helpful.