Undefined variable: mail in _gravatar_get_account_user_picture() (line 183 of

I installed OpenID selector module and Gravatar. If I register with an OpenID, and I receive the following error in many places.

Notice: Undefined variable: mail in _gravatar_get_account_user_picture() (line 183 of /xxx/sites/all/modules/gravatar/gravatar.module).

The following code in function _gravatar_get_account_user_picture has problem:

    if (!empty($account->mail)) {
      return gravatar_get_gravatar($mail);
    }

and it should be:

    if (!empty($account->mail)) {
      return gravatar_get_gravatar($account->mail);
    }