Username is already used - forces logout

[lookbadgers]

Symfony FOSUserBundle versions: 2.1.2 with Symfony 4.4

The user is being incorrectly logged out when trying to change their username to one that already exists. They see the error message The username is already used. but they are logged out and have to login again before trying again.

Steps to reproduce:

1. composer create-project symfony/website-skeleton:^4.4 test
2. composer require friendsofsymfony/user-bundle "~2.1"
3. follow setup https://github.com/FriendsOfSymfony/FOSUserBundle/blob/v2.1.2/Resources/doc/index.rst
4. Create two users
5. Login - fos_user_security_login /login
6. Edit profile - fos_user_profile_edit /profile/edit
7. Change username to other user, the error The username is already used. is displayed and the user is logged out.

[lookbadgers]

Any more information needed? Or is this a user error?