Before saving a new Talk entry I see this warning on a WordPress 5.6 / PHP 7.3: <img width="301" alt="Bildschirmfoto 2021-01-02 um 15 59 48" src="https://user-images.githubusercontent.com/870475/104068247-df9eb880-5204-11eb-9af9-ddcfca4b2f7a.png"> https://github.com/schlessera/as-speaking/blob/master/views/talk-metabox-session.php#L20
Before saving a new Talk entry I see this warning on a WordPress 5.6 / PHP 7.3:
https://github.com/schlessera/as-speaking/blob/master/views/talk-metabox-session.php#L20