Message::getLastMessageHashInTopic

static function getLastMessageHashInTopic(int $topicId): ?string
{
	$res = MessageTable::query()
		->setSelect(['ID', 'POST_MESSAGE_CHECK'])
		->where('TOPIC_ID', '=', $topicId)
		->where('APPROVED', '=', 'Y')
		->setOrder(['ID' => 'DESC'])
		->setLimit(1)
		->exec()
		->fetch()
	;
	return $res ? $res['POST_MESSAGE_CHECK'] : null;
}