new inserted result does NOT have where and conditions

[softwarevamp]

$inserted = $db->categories->insert(array(
'categories_id' => null,
'categories_image' => $json->image,
'parent_id' => $json->parent ? $json->parent->id : 0,
'sort_order' => $json->sort_order,
'date_added' => new DateTime(),
'last_modified' => null
));

$fetched = $db->categories[$inserted['categories_id']];

$inserted's result has no where and conditions but $fetched's has

this affects subsequent referencing table results:
$inserted->categories_description(); // empty
$fetched->categories_description(); //has results

[vrana]

Can you try omitting 'categories_id' => null,?