I couldn't, the game crashed.
I have another error where he doesn't find the 'enemy defeated' screen at the end of the fight now. This one happens both with burglars and the bully in school, and can be ignored.
Weird. I get the error and click ignore. Then it goes on to Billy calling it in.
Have you tried a fresh install where you just copy the save game? Try no mod. Then fight and go to Billy's room. Save, install mod, launch and load.
Ren'py can be wonky. I know when I played Amnety Park (or whatever it's called), I got more errors than I've recieved from all Ren'py games I've ever played. Yet others did not get errors.
I get an error just when the enemy goes down to 0 hp. That's when I hit ignore.
Can you post the error? It's the only way to get a look at what's going on.