Enter that invalid redirect URL into AdminCP > Settings > Options > Site Name/URL/etc > Redirect Domain Whitelist (without the ending / as per the instructions)
You may want to do an .htaccess redirect from
http://www.lagadas.com/ to
https://www.lagadas.com/ (and
http://lagadas.com/ to
https://www.lagadas.com/) so that users can't access the site without an https URL