Failed to register new account

[Guilherme Salgado]

If somebody tries to register a new account using an email that is associated with an existing unvalidated profile, we allow that person to follow the registration proces as if the other profile didn't exist. This works fine when the existing profile has no preferred email, but it crashes (OOPS-292A579) if the email address in question is the profile's preferred email. Since we have a lot of profiles imported from Ubuntu's bugzilla that have a preferred email but are considered invalid because they lack a password, this is happening quite often.