Added fix for issue 2991 to fetch billing and shipping addresses to enable getting a correct price through the (web) API after adding a product to an empty cart

Author: peterjaap

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

@@ -232,6 +232,8 @@ public function createEmptyCart()
         $quote->setShippingAddress($this->quoteAddressFactory->create());
 
         try {
+            $quote->getBillingAddress();
+            $quote->getShippingAddress()->setCollectShippingRates(true);
             $this->quoteRepository->save($quote);
         } catch (\Exception $e) {
             throw new CouldNotSaveException(__('Cannot create quote'));