Error Warning: Invalid argument supplied for foreach()?

Question

WordPress

Hello, tell me what is this error
Warning: Invalid argument supplied for foreach() in /var/www/dzerglib/data/www/foradmins.pp.ua/showman/wp-includes/class-wp-post-type.php on line 597 and
how to remove
it /class-wp-post-type.php on line 597 Warning: Cannot modify header information - headers already sent by (output started at /var/www/dzerglib/data/www/foradmins.pp.ua/showman/wp-includes /class-wp-post-type.php:597) in /var/www/dzerglib/data/www/foradmins.pp.ua/showman/wp-admin/includes/misc.php on line 1114