added string casts - followup of #184

Author: fashxp

src/Security/OAuth/AccountConnector.php

@@ -217,7 +217,7 @@ protected function addTokenData(OAuthTokenInterface $token, OAuthToken $response
                 $value = $this->encryptionService->encrypt($value);
             }
 
-            $token->$setter($value);
+            $token->$setter((string)$value);
         }
     }