Primary links missing with Drupal 6.1, primary links can not be deactivated

Primary links are missing with Drupal 6.1. If they work (older drupal version) they can't be deactivated.

Fix:
Replace this code in the page.tpl.php file:
<?php print theme('menu_links', $primary_links) ?>

With this one, it allows to deactivate the primary links too:

<?php if (isset($primary_links)) : ?>
          <?php print theme('links', $primary_links) ?>
<?php endif; ?>