Thanks for checking it out!
Hmm that does sound odd. When you say "stuck," do you mean that you can't exit it, or the game itself gets stuck? From my attempts just now, I got taken out of fullscreen when I pressed Esc, and could close the crafting window with another press of Esc. If the problem is with the crafting window itself, you should be able to get out of it by opening another window (C, R, or T, for example), and then close from there.
This probably is something connected to the browser, so I'll be looking into ways to get around this (probably with some export settings). As far as I'm aware, there aren't any issues like this in the download version, so you could certainly try that.
Again, thank you for your feedback. =)