The ID field is a field set in protected $pid = "category_id";
By default is not displayed as a column. To display it you need to set 'forced' true.
'forced'=>true |
Display this field, otherwise it is hidden, you can't select it with columns |
'type'=>'number', |
Correct fix how to display this field (as column), not always displayed |
'category_id' => array('title'=> LAN_ID, 'type' => 'number', 'width' =>'5%', 'forced'=> TRUE, 'readonly'=>TRUE),