WooCommerce order product by stock in backend

sortbystock.php

<?php

add_filter('manage_posts_columns', 'mb_add_pdt_stock_columns', 5);

add_action('manage_posts_custom_column', 'mb_add_pdt_stock_columns_display', 5, 2);

add_filter('pre_get_posts', 'mb_add_pdt_stock_columns_query', 999);

add_filter('manage_edit-product_sortable_columns', 'mb_add_pdt_stock_columns_sort');

function mb_add_pdt_stock_columns($defaults){
    
    $defaults['mb_pdt_stock_level'] = __('Stock');
    return $defaults;
}

function mb_add_pdt_stock_columns_display($column_name, $id){
        if($column_name === 'mb_pdt_stock_level'){
        echo get_post_meta( $id, '_stock', true );
    }
}

 
function mb_add_pdt_stock_columns_query($query){
 
        if( !is_admin()
                || !$query->is_main_query()
                || !$query->query['post_type']==='product'
                || !( isset($_GET['orderby']) &&  $_GET['orderby']==='mb_pdt_stock_level' )
                || !isset($_GET['order'])
        ) return;
 
        $order = ( $_GET['order']==='asc' ) ? 'ASC' : 'DESC';
 
        $query->set('meta_query',array(
 
                'relation' => 'OR',
                       
                       
                        array(
                                'key'     => '_stock',
                                'compare' => 'NOT EXISTS',
                                'value' => ''
                        ),
 
 
                        array(
                                'key'     => '_stock',
                                'compare' => 'EXISTS',
                         
                        )
                       
        ));
 
        $query->set('orderby','meta_value_num');
        $query->set('order', $order );
 
}

function mb_add_pdt_stock_columns_sort($sortable){
 
        $sortable['mb_pdt_stock_level'] = 'mb_pdt_stock_level';
        return $sortable;
 
}