show shop instead of 404 page for missing products

by

// Missing product redirect to product category
add_filter( 'rewrite_rules_array', function( $rules )
{
$new_rules = array(
'shop/([^/]*?)/page/([0-9]{1,})/?$' => 'index.php?product_cat=$matches[1]&paged=$matches[2]',
'shop/([^/]*?)/?$' => 'index.php?product_cat=$matches[1]',
);
return $new_rules + $rules;
} );