As an update, I played back through the boss fight again today during a lunch break. I beat Corvo but did not encounter the error again. So not sure what the conditions are that triggered that error.
Hey! Thanks for reporting! We are aware of that crash bug and we will work on a fix. Basically what happens is that the cache is becoming overloaded and the game crashes. It mostly happens after longer play sessions but it seems to kinda also depend on the computer itself because there are also lots of people who can play through the whole game in a row 7-8 hours without the game crashing at all. So when this happens you can just load the last autosave or regular save file and continue the game. But this is really a frustrating bug we need to get fixed. Thanks for reporting and I will continue watch your playtrough! It was fun so far! :D