MC-22813: Changing Quantity and Adding to cart through Quick Order throws exception

- Add guard for getChildren

Author: danmooney2

app/code/Magento/ConfigurableProduct/Plugin/SalesRule/Model/Rule/Condition/Product.php

@@ -56,7 +56,10 @@ private function getProductToValidate(
         $attrCode = $subject->getAttribute();
 
         /* Check for attributes which are not available for configurable products */
-        if ($product->getTypeId() == Configurable::TYPE_CODE && !$product->hasData($attrCode)) {
+        if ($product->getTypeId() == Configurable::TYPE_CODE &&
+            !$product->hasData($attrCode) &&
+            count($model->getChildren())
+        ) {
             /** @var \Magento\Catalog\Model\AbstractModel $childProduct */
             $childProduct = current($model->getChildren())->getProduct();
             if ($childProduct->hasData($attrCode)) {