Fix bug with null result for federated objects

execute.go

@@ -368,6 +368,16 @@ func executorFindInsertionPoints(resultLock *sync.Mutex, targetPoints []string,
 		// get the type of the object in question
 		selectionType := foundSelection.Definition.Type
 
+		if rootValue == nil {
+			if selectionType.NonNull {
+				err := fmt.Errorf("Received null for required field: %v", foundSelection.Name)
+				log.Warn(err)
+				return nil, err
+			} else {
+				return nil, nil
+			}
+		}
+
 		// if the type is a list
 		if selectionType.Elem != nil {
 			log.Debug("Selection should be a list")

http.go

@@ -205,7 +205,7 @@ func (g *Gateway) GraphQLHandler(w http.ResponseWriter, r *http.Request) {
 		// fire the query with the request context passed through to execution
 		result, err = g.Execute(requestContext, plan)
 		if err != nil {
-			results = append(results, formatErrorsWithCode(nil, err, "INTERNAL_SERVER_ERROR"))
+			results = append(results, formatErrorsWithCode(result, err, "INTERNAL_SERVER_ERROR"))
 			continue
 		}