The remote avatar should throw an error when an incorrect image link is supplied, i.e. something like this link to a 404 page on phpbb.com:
https://www.phpbb.com/avatar/55502f40dc8b7c769880b10874abc9d0.jpg

Instead, the avatar system thinks that a proper image has been supplied and updates the user's avatar data to point to this incorrect link. The "image" will not be loaded, however, this leaves us with a broken link to an image that should never happen in the first place.