Does not work with Flathub Steam

Latest, fully updated Fedora 43.

Protontricks returns the following error after selecting a game installed in a Flathub version of Steam:

```
/home/asciiwolf/.var/app/com.github.Matoking.protontricks/cache/protontricks/proton/Proton 10.0/bin/wine cmd.exe /c echo '%AppData%' returned empty string, error message "steam-runtime-launch-client[1231]: W: The --socket option is deprecated. Prefer to use the session bus.
wineserver: using server-side synchronization.
wine: could not load kernel32.dll, status c0000135"
```

Start by reproducing the reported Protontricks error on a fully updated Fedora 43 system with a game installed in Flathub Steam. Verify whether selecting that game still makes the wine command return an empty AppData value and the kernel32.dll error; done means the command completes successfully for that setup.

Written by the indexing model from the issue text.