Issues with favoriting

[parasquared]

Currently, trying to favorite a page yields a couple problems:

1. When saving in a folder that already has the maximum amount of favorites, no error is displayed to the client. Instead, the saving to favorites animation disappears after taking much longer than usual, and the favorite doesn't appear in the folder. (In the next branch, I did push something that at least shows an error to the client, however it's a generic "The item chosen cannot be used." error instead of telling the user they have too many favorites.)
2. Sometimes, the client seems to send back more POST data than it's expecting for the thumbnail, causing the server to also throw an error. (Currently, I have no idea how to consistently trigger this behavior, and the server does try to report this error back to the client also with no success.)