While adding a new page using a classic editor plugin or any plugin which brings older editor back, it will display a critical error but a new page will be added anyway.

Whole Stack trace:

Fatal error: Uncaught ArgumentCountError: Too few arguments to function Kidspress_MetaBox::sanitize(), 1 passed in /site/wp-content/themes/kidspress/inc/metabox.php on line 165 and exactly 2 expected in 
/site/wp-content/themes/kidspress/inc/metabox.php:138 
Stack trace: 
#0 /site/wp-content/themes/kidspress/inc/metabox.php(165): K
idspress_MetaBox->sanitize('sidebar-1') 
#1 /site/wp-includes/class-wp-hook.php(289): Kidspress_MetaBox->save(103) 
#2 /site/wp-includes/class-wp-hook.php(311): 
WP_Hook->apply_filters(NULL, Array) #3 /site/wp-includes/plugin.php(484): WP_Hook->do_action(Array) 
#4 /site/wp-includes/post.php(4309): do_action('save_post', 103, Object(WP_Post), true) 
#5 /site/wp-includes/post.php(4411): wp_insert_post(Array, false, true) 
#6 /site/wp-admin/includes/post.php(419): wp_update_post(Array) #7 /site/wp-admin/post.p in /site/wp-content/themes/kidspress/inc/metabox.php on line 138
, $this->sanitize( wp_unslash( $_POST[ $field ] ) )