fixed a bug assuming that a user object was being passed to the user_name_alter hook.

alt_login.module

@@ -26,7 +26,7 @@ function alt_login_help($route_name, $route_match) {
  * @note there's no easy way to dedupe accounts' display names.
  */
 function alt_login_user_format_name_alter(&$name, AccountInterface $account) {
-  if ($account->isAnonymous() and !$account->isNew()) { // includes accounts tha
+  if ($account->isAnonymous() or ($account instanceof UserInterface and $account->isNew())) {
     // This will be the configured 'anonymous' value
     return;
   }