Update CRUDControllerExtraExportTrait.php

Added missing return statement. Without that you get the following error: *The controller must return a response (null given). Did you forget to add a return statement somewhere in your controller?*

Controller/CRUDControllerExtraExportTrait.php

@@ -16,7 +16,7 @@ public function exportAction(Request $request)
     {
         /* @var CRUDController $this */
         try {
-            parent::exportAction($request);
+            return parent::exportAction($request);
         } catch (\RuntimeException $e) {
             $format = $request->get('format');