yes, minor notice bug, without any consequences.
either disable php notices if it's a production site, or in that line,
change this:
[code:1] function getDisplayRegistration($tab, $user, $ui, $postdata) {[/code:1]
to that:
[code:1] function getDisplayRegistration($tab, $user, $ui, $postdata=null) {[/code:1]
for now (it will work silencing this notice).