drupal_valid_path() uses a variable that is not initialized, nor is a parameter

drupal_valid_path() contains the following code.

$item['link_path']  = $form_item['link_path'];
$item['link_title'] = $form_item['link_title'];
$item['external']   = FALSE;
$item['options'] = '';
_menu_link_translate($item);

$form_item is not a variable initialized from the function, nor one of its parameters.