Invalid argument supplied in taxonomy

1) installed AF 5.x-1.x-dev (2008-Feb-18) [Drupal 5.7]
2) visit /acidfree so that the root album is created
3) visit the newly created root album node/xxx/edit
4) click on Preview. The following warning is logged:

warning: Invalid argument supplied for foreach() in
/var/www/drupal/modules/taxonomy/taxonomy.module on line 32.