FIX #17154 TIME 0:05 Add stamp by default, if no signature modes defined

src/app/user/controllers/UserController.php

@@ -163,7 +163,7 @@ class UserController
                 }
             }
         } else {
-            $body['signatureModes'] = [];
+            $body['signatureModes'] = ['stamp'];
         }
         $body['signatureModes'] = json_encode($body['signatureModes']);