Variable product On Sale filter issue

Resolve variable product on-sale filter issues.

// Fix - Variable product On Sale filter issue
add_filter('advanced_woo_discount_rules_is_on_sale', function($on_sale, $product) {
    if (is_object($product) && method_exists($product, 'get_type')) {
        if ($product->get_type() == 'variable') {
            $on_sale = true;
        }
    }
    return $on_sale;
}, 100, 2);