image module configuration page doesn't validate imagecache presets

(running drupal 5.12)
After enabling ImageCache and ImageCache 4 Image (such a great idea !), I build some preset profiles in admin/build/imagecache and then go to admin/settings/image to activate these presets into Image.

Every time it try to save the configuration, I get an error message "Must specify a width or height." coming from

 function image_settings_sizes_validate(&$form) {
  foreach (element_children($form) as $key) {
    // If there's a label they must provide at either a height or width.
    if ($key != IMAGE_ORIGINAL && !empty($form[$key]['label']['#value'])) {
      if (empty($form[$key]['width']['#value']) && empty($form[$key]['height']['#value'])) {
        form_set_error("image_sizes][$key][width", t('Must specify a width or height.'));
      }
    }
  }
}
 

in image.module

And no changes get saved...

Am I missing something for proper setup of this module ? Since this validation feedback is sensible...

Thanks for your help