Grand ages: Medieval - no polish letters in some places.

**Game information**
Grand Ages: Medieval

**Distribution name and version where applicable**
OpenSUSE Tumbleweed

**Flatpak info**
> flatpak --version
Flatpak 1.6.2
>flatpak --gl-drivers
default
host

**Problem description**
In some places, such like save game dialog, there isn't support for Polish letters. Instead, rectangles are displayed. I don't known it's problem related only to flatpaked version of Steam, related to game, etc. I don't have sufficient amount of disk space to test, sorry.

**Does this issue reproduce with native Steam**
Have not tested