Set it the same as on dev.t.o: "Users can choose to stay in SSL mode after an HTTPS login" disabled as we should always encourage use of SSL. It also simplifies the login form.
Permalink: https://doc.tiki.org/blogpost7-Disabled-Users-can-choose-to-stay-in-SSL-mode-after-an-HTTPS-login-to-have-SSL-login-always-on