Error messages in "under construction" mode
I activated the "under construction" mode of the Be Theme and when I open my website, text and title are shown at the very bottom of the page and above there are several error messages:
Warnung: trying to access array offset on value of type null in /var/www/vhosts/.../wordpresscontent/themes/betheme/functions/theme-head.php on line 433
Same warning concerning line 434, 722, 1734, 1735.
Where do these error messages come from and how can I remove them?