Undefined property error in pop-up player in 5.2.0

I recently upgraded a 3.x test site to 3.3.0 and sermon Speaker component to 3.2.0. When I click on a single sermon link, which should activate the player pop-up, I am getting the following error message:

Notice: Undefined property: stdClass::$sermon_title in /home/www/vac.golgota.hu/www/components/com_sermonspeaker/views/sermon/tmpl/protostar.php on line 44

I didn't work on this test site for a considerable amount of time before these recent upgrades, so I don't know if the problem existed before, or had something to do with these upgrades.

here is the site link:
vac.golgota.hu.2.golgota.hu/index.php/me...enu/tanitasokarticle

The site is in Hungarian, but if you click on any of the series, and then one of the linked sermon titles, the error appears.

Thanks for all the work you do on this component.

The protostar layouts aren't part of the 5.2.0 release. Maybe it wasn't properly deleted on the update.
Just try with a different one (like content or icon) for the sermon detailpage.
This should likely fix it.