Display error if API server responsed with incorrect code

Classes/Controller/RecommenderController.php

@@ -115,6 +115,9 @@ class RecommenderController extends AbstractController
                     $this->cache->set('result_subject', $result->subject);
 
                     $this->assignViewVariables();
+                } else {
+                    $this->logger->error('Server response error: '.$response->getStatusCode());
+                    $this->view->assign('error','Server response error: '.$response->getStatusCode());
                 }
             } catch (\Exception $e) {
                 $this->logger->error('Request error: '.$e->getMessage());