Mandatory for 1.0, 1.01 and 1.02 versions! The patch fixes a major crash in the late game.
Replace the gent folder from
Amnesia - The Dark Descent\redist\custom_stories\Secret Darkfire Project\entities\from_MFP\gent
With the one provided. Your game saves should work fine, but you might need to load one from before entering the Rift map.