[TYPO3-dam] emty table tx_dam_mm_ref

[Stephan Petzl]

what is the tx_dam_mm_ref table for?
the hl_dam_gallery generates a query, but nothing returns, and that is 
because there is not a single record in this table.
any ideas why`?

query:
SELECT tx_dam_mm_ref.sorting, tx_dam.file_name, tx_dam.file_path, 
tx_dam.tx_hldamgallery_viewcount
FROM tx_dam_mm_ref, tx_dam
WHERE
tx_dam.uid=tx_dam_mm_ref.uid_local and tx_dam_mm_ref.uid_foreign=52 and 
tx_dam_mm_ref.sorting = 3

BR Stephan