Auth type warning during registration

on Mahara master (1.6.0dev)

When I register on the site (internal auth; tried with confirm registration and without), I get the following warning:

[WAR] 49 (auth/lib.php:2178) Undefined index: authtype
Call stack (most recent first):

    log_message("Undefined index: authtype", 8, true, true, "/home/kristina/code/16stable/htdocs/auth/lib.php", 2178) at /home/kristina/code/16stable/htdocs/lib/errors.php:446
    error(8, "Undefined index: authtype", "/home/kristina/code/16stable/htdocs/auth/lib.php", 2178, array(size 4)) at /home/kristina/code/16stable/htdocs/auth/lib.php:2178
    auth_register_submit(object(Pieform), array(size 10)) at Unknown:0
    call_user_func_array("auth_register_submit", array(size 2)) at /home/kristina/code/16stable/htdocs/lib/pieforms/pieform.php:512
    Pieform->__construct(array(size 11)) at /home/kristina/code/16stable/htdocs/auth/lib.php:2061
    auth_generate_registration_form_js(array(size 11), array(size 4)) at /home/kristina/code/16stable/htdocs/register.php:209