Hi,
That was kind of an experimental thing, I can't say that it works that great.
But, to avoid that script error go into Site Settings > Security tab and check the box that says "Show Password Strength On Registration Page?"
That should fix it but the password strength meter is still not that great because it is mainly going by password length and it says it is strong if it meets a certain length so I'm not sure how useful you will find it.
Hope that helps,
Joe