Tokens not expiring

Not sure if others have this issue, but thought I'd paste here to help. We had 2.5 million of these sitting in the database.

What causes this is if the node which owns the token is removed, then the cron for the token module for some reason creates a new token for it, forever and ever. So we had literally millions of unexpired tokens in the database going back years. Not something I want to spend too much time on, but I've quickly modified the cron function to the below. I've set the limit to 100 so as not to kill the cron.

/**
 * Implements hook_cron().
 */
function review_token_cron() {
  $n_expired = 0;
  $removed_expired = [];

  $expired = db_select('node_preview_tokens', 't')
    ->fields('t')
    ->where('expires < UNIX_TIMESTAMP(NOW())')
    ->range(0, 100)
    ->execute()->fetchAll();

  foreach ($expired as $e) {
    $node = node_load($e->nid);
    if ($node) {
      $token = new PreviewToken($node);
      $token->expireToken();
    }
    else {
      $removed_expired[] = $e->token;
    }
    $n_expired++;
  }

  if (count($removed_expired) > 0) {
    $deleted = db_delete('node_preview_tokens')
      ->condition('token', $removed_expired, 'IN')
      ->where('expires < UNIX_TIMESTAMP(NOW())')
      ->execute();

    watchdog('Content Publish Review', 'Cron: %n_expired %pl_tokens orphan expired.',
      array(
        '%n_expired' => $deleted,
        '%pl_tokens' => format_plural($deleted, 'token', 'tokens'),
      ),
      WATCHDOG_NOTICE
    );
  }

  if ($n_expired) {
    watchdog('Content Publish Review', 'Cron: %n_expired %pl_tokens expired.',
      array(
        '%n_expired' => $n_expired,
        '%pl_tokens' => format_plural($n_expired, 'token', 'tokens'),
      ),
      WATCHDOG_NOTICE
    );
  }
}