ENGCOM-4416: Notice: Undefined index: shipping_carrier_code is return…

…ed instead of Required parameter 'shipping_carrier_code' is missin #405

 - Merge Pull Request magento/graphql-ce#405 from XxXgeoXxX/graphql-ce:2.3-develop#400
 - Merged commits:
   1. 0ae6146
   2. 86857b3
   3. 63f4cfb
   4. 2f3fdc3

app/code/Magento/QuoteGraphQl/Model/Resolver/SetShippingMethodsOnCart.php

@@ -67,13 +67,13 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
 
         $shippingMethod = reset($shippingMethods); // This point can be extended for multishipping
 
-        if (!$shippingMethod['cart_address_id']) {
+        if (!isset($shippingMethod['cart_address_id']) || empty($shippingMethod['cart_address_id'])) {
             throw new GraphQlInputException(__('Required parameter "cart_address_id" is missing'));
         }
-        if (!$shippingMethod['carrier_code']) {
+        if (!isset($shippingMethod['carrier_code']) || empty($shippingMethod['carrier_code'])) {
             throw new GraphQlInputException(__('Required parameter "shipping_carrier_code" is missing'));
         }
-        if (!$shippingMethod['method_code']) {
+        if (!isset($shippingMethod['method_code']) || empty($shippingMethod['method_code'])) {
             throw new GraphQlInputException(__('Required parameter "shipping_method_code" is missing'));
         }