When you only have "No institution" on your site and both "Registration allowed" and "Confirm registration" turned on (but also only "Registration allowed"), you get the following warning message:
[WAR] f9 (auth/lib.php:2147) Undefined index: authtype
Call stack (most recent first):
log_message("Undefined index: authtype", 8, true, true, "/var/www/maharadev/code/htdocs/auth/lib.php", 2147) at /var/www/maharadev/code/htdocs/lib/errors.php:446
error(8, "Undefined index: authtype", "/var/www/maharadev/code/htdocs/auth/lib.php", 2147, array(size 4)) at /var/www/maharadev/code/htdocs/auth/lib.php:2147
auth_register_submit(object(Pieform), array(size 10)) at Unknown:0
call_user_func_array("auth_register_submit", array(size 2)) at /var/www/maharadev/code/htdocs/lib/pieforms/pieform.php:514
Pieform->__construct(array(size 11)) at /var/www/maharadev/code/htdocs/auth/lib.php:2030
auth_generate_registration_form_js(array(size 11), array(size 0)) at /var/www/maharadev/code/htdocs/register.php:209
This did happen if every institutions only use Internal auth.