That... is admittedly a new one. Hmm. I know when first loading the browser version it would very rarely give the error, but I assumed it was the player because upon refresh and every other attempt the error doesn't appear. Out of curiosity do you know where you saved? I'll add it as a bug to the boars. I'm sorry you experienced that I believe you found a rarer bug!
Edit: It's also such a shock to see plugin creators I've respected for awhile playing my game. It really is an honor.