Prevent wrong login

[DuncanNaves]

When typing incorrect credentials, user is facing a 404 without possibility to roll back to login screen.
The idea would be to add a button to clear saved credentials from the browser so that the user can type again his credentials.

[Berdir]

Kind of the similar can happen if you log in with valid credentials but they are not properly set up (= not have an active version), then you just get an empty page and an error pops up about there not being an active version.