Bug: while attempting to send a PM, the "to" form get's cleared-out and getting the "The to field cannot be empty" error

Expected behavior: Sending the PM to other person

Actual behavior: Recieving error described in the "bug" section of this post

Steps to duplicate: Try to send PM to user pokehidden

The user Pokehidden doesn't exist. (Check here)

Do you have the user profile of the person you'd like to contact on a link? If yes copy the name from there because there might be some strange spelling inside.

Past that are you sure you saw pokehidden as a user's name, and not just as a tag?

Last but not least the official bug report thread is here.