The "Exception Occurred" to me too in this same scenario. I think it is just one of the story endings.
I played the whole game in ubuntu xenial on x86_64 cpu (running ./DDLC.sh), with no issues at all but this, which is showing as no-turning-back.
Aside from the exception message itself, never nice to see, the game suffered from errors from that time on. The main menu entries became corrupted, so I had to quit the game. Launched the game once again, and I saw the same font corruption, further the program deleted ALL my saved games AND no new games can be started because the engine says one of the character files is corrupted (can't remember the exact warning).
I would like to help developers but I currently don't know how to attach the traceback text file created by the game.