Checkboxes with select or other display empty element

The following commit broke select elements with "Multiple" and "Other option" enabled. The form element shows only the title, no checkboxes are displayed.

http://drupalcode.org/project/webform.git/commitdiff/90af819b4e10d774b1a...

The code that I am confused about that was added in that change is:

  // Sanitize the options in Select or other check boxes and radio buttons.
  if ($element['#select_type'] == 'checkboxes') {
    $element['select']['#process'][] = 'webform_expand_select_ids';
  }
  elseif ($element['#select_type'] == 'radios') {
    $element['select']['#select_type'] = array('expand_radios', 'webform_expand_select_ids');
  }

I don't understand why for checkboxes the #process key is changed, while for radios the #select_type key is changed. That last change seems very strange, it looks like it should be #process. But the main reason why the code did not work was that there is no expand_checkboxes (or webform_expand_checkboxes or select_or_other_expand_checkboxes, I don't know which one should be used).