$form['menu'] not set in localizermenu_form_alter()

When editing a translation of a node the following error is presented:

warning: reset() [function.reset]: Passed variable is not an array or object in /Users/fuerst/Sites/projekte/Drupal/drupal-5.3-localizer/sites/all/modules/localizer/localizer.module on line 1197.
warning: Variable passed to each() is not an array or object in /Users/fuerst/Sites/projekte/Drupal/drupal-5.3-localizer/sites/all/modules/localizer/localizer.module on line 1198.

I tracked it down to line 146 in localizer/modules/localizernode.module:
$form['localizernode_menu'] = $form['menu'];

The Array $form['menu'] is not set at this point.

I'm using Drupal 5.3, 5.x-1.x-dev (2007-Nov-28) and localizer-sites-all-5.3-1.11.tgz.

Regards,
Bernhard