MC-19746: The shipping address contains null values when there's no shipping address set on a cart

- return null instead of fields when there's no selected method

Author: cpartica

app/code/Magento/QuoteGraphQl/Model/Resolver/ShippingAddress/SelectedShippingMethod.php

@@ -64,14 +64,7 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
                 ],
             ];
         } else {
-            $data = [
-                'carrier_code' => null,
-                'method_code' => null,
-                'carrier_title' => $carrierTitle,
-                'method_title' => $methodTitle,
-                'amount' => null,
-                'base_amount' => null,
-            ];
+            $data = null;
         }
         return $data;
     }