The Journey Down Chapter Two/Three segfault on launch

**Game information**
[The Journey Down: Chapter Three](https://store.steampowered.com/app/579760/The_Journey_Down_Chapter_Three/)

**Distribution name and version where applicable**
Silverblue 30.

**Flatpak info**

```
$ flatpak --version
Flatpak 1.2.4
$ flatpak --gl-drivers
flatpak --gl-drivers
default
host
```

**Problem description**
Simple segfault on launch:
```
$ ./JourneyDown3
Data directory: /home/jurf/.config/JourneyDownThree Archive path: /var/home/data/games/steamapps/common/The Journey Down Chapter Three/jd3.gob

Initializing Theoraplayer Video Playback Library (2.0)
- libtheora version: Xiph.Org libtheora 1.2.0alpha 20100924 (Ptalarbvorm)
- libvorbis version: Xiph.Org libVorbis 1.3.4
------------------------------------
Changing number of worker threads to: 1
Starting The Journey Down: Chapter 3.09
Segmentation fault (core dumped)
```

Coredump: [core.JourneyDown3.1000.243015d27cac419c9297e769bb42f312.17480.1554733905000000.zip](https://github.com/flathub/com.valvesoftware.Steam/files/3056178/core.JourneyDown3.1000.243015d27cac419c9297e769bb42f312.17480.1554733905000000.zip)

**Does this issue reproduce with native Steam**
Have not tested, though probably not, because I played Chapter Two on native Steam and it worked fine, but doesn’t work in Flatpak.