Accidentaly i found this method, this way the database hacker can't steal your stuff but it makes your life a bit more complicated.
The trick is simple and easy. Choose a password longer than 16 characters.
Here comes the trick : The website can handle the password while the game simply can't. Anything you write the login screen - invalid. If you write the long pass that's why, if you cut to 16 chars then that's why. So, by this way you can log in to the website, but can't log in to the game. Neither the hacker unless he cracks your mailbox as well.
Pretty good method to protect your inactive/mule accounts against anyone.