Merging cancelled bookings causes issues with display/reporting

Steps to replicate:
Make an event booking with priceset options..
Cancel that booking by editing and cancelling it.

Make an event booking with the similar contact details..

Merge the two records including the contributions/participant records.

The first participant record will still have the fee levels but no line items.
The other participant records will have the fee level and line items.

This causes the layout of the fee levels to break when viewing a participant.
It also causes odd reporting numbers as some reports count by fee level.. and some count line items and some count both. (i.e. if a fee level doesn't have a line item associated with it, some event reports count it anyway)

We used this SQL to detect broken participant records:
SELECT * FROM civicrm_line_item RIGHT JOIN civicrm_participant ON civicrm_participant.id = civicrm_line_item.entity_id WHERE civicrm_participant.event_id = 1 AND civicrm_line_item.id IS NULL

A specific event ID is used to just look at each event separately.