magento/magento2#12993: Type error in Cart/Totals [Forwardport for public PR#9647]

app/code/Magento/Quote/Model/Cart/CartTotalRepository.php

@@ -10,6 +10,7 @@ use Magento\Quote\Api\CartRepositoryInterface;
 use Magento\Quote\Api\CartTotalRepositoryInterface;
 use Magento\Catalog\Helper\Product\ConfigurationPool;
 use Magento\Framework\Api\DataObjectHelper;
+use Magento\Framework\Api\ExtensibleDataInterface;
 use Magento\Quote\Model\Cart\Totals\ItemConverter;
 use Magento\Quote\Api\CouponManagementInterface;
 
@@ -94,6 +95,7 @@ class CartTotalRepository implements CartTotalRepositoryInterface
             $addressTotalsData = $quote->getShippingAddress()->getData();
             $addressTotals = $quote->getShippingAddress()->getTotals();
         }
+        unset($addressTotalsData[ExtensibleDataInterface::EXTENSION_ATTRIBUTES_KEY]);
 
         /** @var \Magento\Quote\Api\Data\TotalsInterface $quoteTotals */
         $quoteTotals = $this->totalsFactory->create();