Errors after WP5.3 update

Replies: 0

After upgrading to WP5.3, some errors are shown on the “Create new …” page:

Warning: strlen() expects parameter 1 to be string, object given in /home/www/wordpress/wp-includes/formatting.php on line 3380

Warning: strlen() expects parameter 1 to be string, object given in /home/www/wordpress/wp-includes/formatting.php on line 3380

Warning: strlen() expects parameter 1 to be string, object given in /home/www/wordpress/wp-includes/formatting.php on line 3380

Warning: Cannot modify header information - headers already sent by (output started at /home/www/wordpress/wp-includes/formatting.php:3380) in /home/www/wordpress/wp-admin/admin-header.php on line 9

I’m pretty sure, that the issue is with Graphene, since deactivating all Plugins doesn’t fix the issue, but changing the theme does.
The rest of the website looks just fine, but I’d still be glad if this was fixed.
Looking forward to your respond 🙂