Deleting trouble ticket leaves comments to database (vtiger 6.4)

Hello,

When deleting ticket it goes to the trash bin. When deleting ticket from trashbin, it leaves the ticket comments to the database.

Made the following test:

1. Added ticket (internal ticket id : 18177)
2. Added a couple of comments (comments saved to vtiger_modcomments table, related_to value 18177)
3. Deleted ticket
4. Deleted ticket from trash bin
5. Checked the database, the ticket was deleted. Comments were still in vtiger_modcomments -table (found with query using related_to = 18177)

Should the final ticket delete also delete all related data to that ticket? Otherwise the database will end up having garbage data.