This is because you're using PaperScript. I should improve error handling in those cases. There's probably an error on your PaperScript on line 73!
> --
> You received this message because you are subscribed to the Google Groups "Paper.js" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to
paperjs+u...@googlegroups.com.
> For more options, visit
https://groups.google.com/groups/opt_out.
> <paper error.PNG>