Version::getPrevious

private function getPrevious()
{
	$versions = static::getModelList(array(
		'filter' => array(
			'OBJECT_ID' => $this->objectId,
			' $this->id,
		),
		'order' => array(
			'ID' => 'DESC',
		),
		'limit' => 1
	));
	return array_shift($versions)?: null;
}