Infinite redirects after changing registry in username

Hello!

A user with name "user" changed his name to "User" on the master site. After that, he can't login on any subsite. He gets infinite redirects with messages in log:

• Session opened for user.
• Session closed for user.
• Session opened for user.
• Session closed for user.
• ...

User tries to login from a subsite. It redirects him to the master site, it logins user as "User" and redirects to subsite. The subsite checks cookies, load info from the database (without case-sensitive) and authorize the user. After reloading page, PHP checks

$user->name !== $cookie['name'] 

and logout user because "user" !== "User".

I added the patch to fix it. Verify it, please.
Thank you!