fix empty customer id on customer cart

fix_empty_customer_id_on_customer_cart.patch

Index: vendor/magento/module-quote/Model/QuoteManagement.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- src/vendor/magento/module-quote/Model/QuoteManagement.php	(date 1568972641000)
+++ src/vendor/magento/module-quote/Model/QuoteManagement.php	(date 1568972665300)
@@ -543,7 +543,7 @@
     }
 
     /**
-     * Prepare quote for customer order submit
+     * Prepare address for customer quote.
      *
      * @param Quote $quote
      * @return void
@@ -563,41 +563,69 @@
         if ($shipping && !$shipping->getSameAsBilling()
             && (!$shipping->getCustomerId() || $shipping->getSaveInAddressBook())
         ) {
-            $shippingAddress = $shipping->exportCustomerAddress();
-            if (!$hasDefaultShipping) {
-                //Make provided address as default shipping address
-                $shippingAddress->setIsDefaultShipping(true);
-                $hasDefaultShipping = true;
-                if (!$hasDefaultBilling && !$billing->getSaveInAddressBook()) {
-                    $shippingAddress->setIsDefaultBilling(true);
-                    $hasDefaultBilling = true;
-                }
-            }
-            //save here new customer address
-            $shippingAddress->setCustomerId($quote->getCustomerId());
-            $this->addressRepository->save($shippingAddress);
-            $quote->addCustomerAddress($shippingAddress);
-            $shipping->setCustomerAddressData($shippingAddress);
-            $this->addressesToSync[] = $shippingAddress->getId();
-            $shipping->setCustomerAddressId($shippingAddress->getId());
+            if ($shipping->getQuoteId()) {
+                $shippingAddress = $shipping->exportCustomerAddress();
+            } else {
+                $defaultShipping = $this->customerRepository->getById($customer->getId())->getDefaultShipping();
+                if ($defaultShipping) {
+                    try {
+                        $shippingAddress = $this->addressRepository->getById($defaultShipping);
+                        // phpcs:ignore Magento2.CodeAnalysis.EmptyBlock
+                    } catch (LocalizedException $e) {
+                        // no address
+                    }
+                }
+            }
+            if (isset($shippingAddress)) {
+                if (!$hasDefaultShipping) {
+                    //Make provided address as default shipping address
+                    $shippingAddress->setIsDefaultShipping(true);
+                    $hasDefaultShipping = true;
+                    if (!$hasDefaultBilling && !$billing->getSaveInAddressBook()) {
+                        $shippingAddress->setIsDefaultBilling(true);
+                        $hasDefaultBilling = true;
+                    }
+                }
+                //save here new customer address
+                $shippingAddress->setCustomerId($quote->getCustomerId());
+                $this->addressRepository->save($shippingAddress);
+                $quote->addCustomerAddress($shippingAddress);
+                $shipping->setCustomerAddressData($shippingAddress);
+                $this->addressesToSync[] = $shippingAddress->getId();
+                $shipping->setCustomerAddressId($shippingAddress->getId());
+            }
         }
 
         if (!$billing->getCustomerId() || $billing->getSaveInAddressBook()) {
-            $billingAddress = $billing->exportCustomerAddress();
-            if (!$hasDefaultBilling) {
-                //Make provided address as default shipping address
-                if (!$hasDefaultShipping) {
-                    //Make provided address as default shipping address
-                    $billingAddress->setIsDefaultShipping(true);
-                }
-                $billingAddress->setIsDefaultBilling(true);
-            }
-            $billingAddress->setCustomerId($quote->getCustomerId());
-            $this->addressRepository->save($billingAddress);
-            $quote->addCustomerAddress($billingAddress);
-            $billing->setCustomerAddressData($billingAddress);
-            $this->addressesToSync[] = $billingAddress->getId();
-            $billing->setCustomerAddressId($billingAddress->getId());
+            if ($billing->getQuoteId()) {
+                $billingAddress = $billing->exportCustomerAddress();
+            } else {
+                $defaultBilling = $this->customerRepository->getById($customer->getId())->getDefaultBilling();
+                if ($defaultBilling) {
+                    try {
+                        $billingAddress = $this->addressRepository->getById($defaultBilling);
+                        // phpcs:ignore Magento2.CodeAnalysis.EmptyBlock
+                    } catch (LocalizedException $e) {
+                        // no address
+                    }
+                }
+            }
+            if (isset($billingAddress)) {
+                if (!$hasDefaultBilling) {
+                    //Make provided address as default shipping address
+                    if (!$hasDefaultShipping) {
+                        //Make provided address as default shipping address
+                        $billingAddress->setIsDefaultShipping(true);
+                    }
+                    $billingAddress->setIsDefaultBilling(true);
+                }
+                $billingAddress->setCustomerId($quote->getCustomerId());
+                $this->addressRepository->save($billingAddress);
+                $quote->addCustomerAddress($billingAddress);
+                $billing->setCustomerAddressData($billingAddress);
+                $this->addressesToSync[] = $billingAddress->getId();
+                $billing->setCustomerAddressId($billingAddress->getId());
+            }
         }
         if ($shipping && !$shipping->getCustomerId() && !$hasDefaultBilling) {
             $shipping->setIsDefaultBilling(true);