In the file backup.php there is the array tables.
$tables = array('admin','alias','config','domain','domain_admins','log','mailbox','vacation');
if i am right it should also contain the vacation_notification table
Logged In: YES
Well, the vacation_notification table is not critical (the worst thing that can happen is that someone receives another autoreply when sending the next mail), but basically you are right ;-)
Thanks for reporting this!
Fixed in SVN r282.