Non-ASCII guest author names cannot be added to post

I created a guest author and he gets a slug containing non-ASCII characters (Cyrillic in my case). Then I tried to add him to some post. I was able to select him, but after saving the post the author list didn’t change.

There are 2 issues leading to this. First, the encode() function used in co-authors-plus.js doesn’t work well with non-ASCII characters, at least in Chrome. I’ve changed it to decodeURIComponent() and now it’s better. And second, when searching for guest user, the plugin doesn’t find him because it tries to search by the raw, non-url-encoded slug.

Here is the patch that tries to address both issues (works for me).

https://wordpress.org/plugins/co-authors-plus/