bug#42552: 28.0.50; Overlay 'face' property doesn't set the "underlying face" for 'after-string'

[Eli Zaretskii]

> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Sun, 26 Jul 2020 21:23:32 +0300
> 
> The reproduction scenario is almost the same, only in this case the 
> problem occurs when the *end* of the overlay falls on a position with
> the non-nil 'extend' property (and the overlay is 10 lines long).
> See the screenshots.
> 
> Please let me know if you need any further clarifications.

I'd like a recipe for reproducing the problem and the description of
what exactly constitutes the problem, if possible.

Thanks.