editor/new: submit empty form block Publish Article button

[peernohell]

Hi,

Thanks you so much for you work ❤️
On the demo website, I wanted to see which errors will popup if I submit an empty form for a new article.

When I do that the Publish Article button become disabled and never become enable.
I also notice in the console that a promise exception was uncaught.

Uncaught (in promise) Error: Request failed with status code 422

Certainly that the submit function didn't catch the promise and show errors.

If you want to reproduce, go to https://next-realworld.now.sh/editor/new login then submit the form without filling anything.

If you need more information feel free to ask :)