Please update the GoG version with the hotfix. Thanks.
I've been trying to release updates on GOG every few hours since yesterday, but they're experiencing issues with uploading and downloading (and apparently there's some sort of corruption of uploaded builds?).
I'll try it again right now and see if it's working.
EDIT: Still no dice, waiting for support to get more information or ETA. In the meantime, you can PM me proof of purchase, I can send you a Steam key -- both versions are DRM-free, and save files are compatible between versions, so you can download it and continue playing.