Ooooh shit, my bad! I initially thought no quest progress needs more than 16 bit, have totally forgotten about American Dream.
I couldn't figure out what's crashing there.
I've added a new crash report feature that catches those kind of crashes too. Could you do me a favor and try it one more time with the 1.5.9 version?
It should crash again, but hopefully this time with a stack trace pointing at the problem.