#12705: Integrity constraint violation error after reordering product with custom options

- Fixed issue by updating options if parent item is same for more than one product
- Fixed issue for reorder in admin while checking the availability of product, which is not available in case of associate product.

Author: vinayshah

app/code/Magento/ConfigurableProductSales/Model/Order/Reorder/OrderedProductAvailabilityChecker.php

@@ -45,7 +45,7 @@ public function __construct(
     public function isAvailable(Item $item)
     {
         $buyRequest = $item->getBuyRequest();
-        $superAttribute = $buyRequest->getData()['super_attribute'];
+        $superAttribute = isset($buyRequest->getData()['super_attribute']) ? $buyRequest->getData()['super_attribute'] : [];
         $connection = $this->getConnection();
         $select = $connection->select();
         $orderItemParentId = $item->getParentItem()->getProductId();

app/code/Magento/Quote/Model/Quote/Item.php

@@ -745,6 +745,9 @@ public function saveItemOptions()
                 unset($this->_options[$index]);
                 unset($this->_optionsByCode[$option->getCode()]);
             } else {
+                if (!$option->getItem() || !$option->getItem()->getId()) {
+                    $option->setItem($this);
+                }
                 $option->save();
             }
         }