Registration configuration not properly taken into account in close wiki

Reproduction steps:

• Create a fresh wiki
• Login with Admin and setup the right to prevent unregistered users to view it
• In Administration > Registration force using a captcha to register, and to have a password of at least 12 characters
• Logout and go to <yourwiki>/register/
• Try to register a user with a password of 6 characters

Expected result:

• this should be prevented even before the form is sent because the password is of 6 characters, the captcha should be shown

Obtained result:

• the form can be sent, and no captcha is shown. The user cannot register though because it's missing a captcha..