bug#35273: "Marker does not point anywhere" when reading next article

[Noam Postavsky]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Noam Postavsky <npostavs@gmail.com>
>> Date: Tue, 16 Apr 2019 09:56:36 -0400
>> Cc: "Basil L. Contovounesios" <contovob@tcd.ie>, 35273@debbugs.gnu.org
>> 
>> Oh right, OVERLAY_POSITION calls marker_position.  I think the patch
>> below should paper over the problem, but I'm not sure if it's the right
>> thing.
>
> I think it would be better to try to understand how we got such an
> overlay.  Was it deleted, per chance?

I entirely agree with this, but how to check for that?