Proper handling of Ajax exceptions

modules/cms/classes/Controller.php

@@ -13,7 +13,7 @@
 use Session;
 use Request;
 use Response;
-use Exception;
+use Throwable;
 use SystemException;
 use BackendAuth;
 use Twig\Environment as TwigEnvironment;
@@ -778,8 +778,8 @@ protected function execAjaxHandlers()
                 $responseContents['X_WINTER_ERROR_MESSAGE'] = $ex->getMessage();
                 throw new AjaxException($responseContents);
             }
-            catch (Exception $ex) {
-                throw $ex;
+            catch (Throwable $ex) {
+                throw new SystemException(Lang::get('cms::lang.ajax_handler.error_occurred'), previous: $ex);
             }
         }
 

modules/cms/lang/en/lang.php

@@ -169,6 +169,7 @@
     'ajax_handler' => [
         'invalid_name' => 'Invalid AJAX handler name: :name.',
         'not_found' => "AJAX handler ':name' was not found.",
+        'error_occurred' => 'An error occurred while executing the AJAX handler.',
     ],
     'cms' => [
         'menu_label' => 'CMS',