Just wondering since there's no changelog attached and usually someone posts the contents in the forums.
Assuming it's bugfixes, but curious because I played for hours yesterday and hoping there's not a chance of breaking saves.

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Even if it is a bit late - i took my Steam savegames (finished the game there years ago) and pulled them over onto my GOG version folder. I was able to load my savegames without any problems.
The game unlocks i achieved while playing the steam version back then weren't unlocked though.

So i would say there is no risk of breaking your saves if you upgrade. Don't forget that you can downgrade game versions here on GOG which i really think is a great feature.