Scratch-www: Comments can’t handle unsupported characters

[Kenny2github]

It seems like unsupported characters like emoji aren’t handled well:

My take on the logic here is:

1. It checks if it’s an empty comment
2. It removes unsupported characters
3. It realizes that it’s empty now and freaks out and also does weird stuff

Originally reported in https://scratch.mit.edu/discuss/post/2771368/ (deathly hallows is my alt)

[thisandagain]

We'll handle this during the redesign of comments next year.