Civicrm_line_item table not cleaned up after delete process

Originally filed in forum: http://forum.civicrm.org/index.php?topic=20885.new;topicseen#new

The civicrm_line_item table does not delete records when the contact records no longer exist.

Here's the sequence of events to reproduce the case.

1. Create an event registration with multiple registrants in test mode. 1 paying registrant with 2 guests.
2. Delete the event registration records from the guest contact records.
3. Permanently delete the guest contact records.
4. Delete the original or paying registrant's event registration record. Note: The line_item record from this record is deleted from the line_item table....HOWEVER
5. The guest records are not deleted from the line_item table. Note: The guest participant records are deleted from the participant table.

The result is that there are 2 orphaned records that now reside in the civicrm_line_item table. Let me know if there is somewhere else this should be posted.