[Security/Core] UserInterface::getPassword() can return null

src/Symfony/Component/Security/Core/User/UserInterface.php

@@ -55,7 +55,7 @@ interface UserInterface
      * This should be the encoded password. On authentication, a plain-text
      * password will be salted, encoded, and then compared to this value.
      *
-     * @return string The password
+     * @return string|null The encoded password if any
      */
     public function getPassword();