Event with no fees shows the fees section with just the word "Total" on the register page
And says Undefined array key "quickConfig".
It doesn't affect registration, but is obviously wrong. In 5.71 caused by https://github.com/civicrm/civicrm-core/pull/29197 (yes the one I just merged 2 minutes ago - I figured it was better to get the waitlist fix in).