MC-32655: (GraphQL) Set default value of save_in_address_book to true when no value is specified

- Fixed code as per new review comments

Author: avattam06

app/code/Magento/QuoteGraphQl/Model/Cart/SetBillingAddressOnCart.php

@@ -57,7 +57,7 @@ public function execute(ContextInterface $context, CartInterface $cart, array $b
         $customerAddressId = $billingAddressInput['customer_address_id'] ?? null;
         $addressInput = $billingAddressInput['address'] ?? null;
 
-        if ($addressInput) {
+        if (!$customerAddressId && $addressInput) {
             $addressInput['save_in_address_book'] = isset($billingAddressInput['address']['save_in_address_book'])
                 ? (bool) $billingAddressInput['address']['save_in_address_book'] : true;
         }

app/code/Magento/QuoteGraphQl/Model/Cart/SetShippingAddressesOnCart.php

@@ -48,12 +48,11 @@ public function execute(ContextInterface $context, CartInterface $cart, array $s
                 __('You cannot specify multiple shipping addresses.')
             );
         }
-        $shippingAddressInput = current($shippingAddressesInput) ?? null;
+        $shippingAddressInput = current($shippingAddressesInput) ?? [];
         $customerAddressId = $shippingAddressInput['customer_address_id'] ?? null;
 
-        if ($shippingAddressInput && !$customerAddressId) {
-            $shippingAddressInput['address']['save_in_address_book'] = isset($shippingAddressInput['address']['save_in_address_book'])
-                ? (bool) $shippingAddressInput['address']['save_in_address_book'] : true;
+        if (!$customerAddressId && !isset($shippingAddressInput['address']['save_in_address_book'])) {
+            $shippingAddressInput['address']['save_in_address_book'] = true;
         }
 
         $shippingAddress = $this->getShippingAddress->execute($context, $shippingAddressInput);