Error "User not found" when the recipient is selected from list by the mouse

Steps to reproduce:
1. Log in to forum
2. Go to "Messages"
3. Press "Compose"
4. Enter 2 first symbols of a recipient, for example "Ал" and from list pick "Александр Вершинин" by mouse.

Actual result: Field "To" is highlighted in red and error "User not found" appears. If you change focus to another field the error disappears.
Expected result: User added to the field "To" (recipient) without any error.