Can't use VST, Wine flatpak is installed

### System Information

Steam OS

### LMMS Version(s)

latest nightly appimage

### Most Recent Working Version

_No response_

### Bug Summary

VeSTiege doesn't open VSTs, screen temporarily freezes when given a VST file.

### Expected Behaviour

VeSTiege should open the VST using the WINE flatpak

### Steps To Reproduce

VeSTiege doesn't open VSTs, screen temporarily freezes when given a VST file.

### Logs

### Screenshots / Minimum Reproducible Project

_No response_

### Please search the issue tracker for existing bug reports before submitting your own.

- [x] I have searched all existing issues and confirmed that this is not a duplicate.

Start by reproducing the VeSTiege failure on SteamOS with the latest nightly AppImage and a VST file, then inspect the code path that launches the WINE flatpak. Done means VeSTiege opens the VST through the installed WINE flatpak without freezing the screen.

Written by the indexing model from the issue text.