Queue with only dynamic agents -Join & Leave empty?

Dear folks,

I am setting up a queue with dynamic agents only and have a problem with Join & leave empty.
When an agent logs off with *12 without logging off the queue, it seems like the queue application depends on the extension hint to be nonexistent.
E.g. [email protected]

However, for BLF reasons I replace the state with an UNAVAILABLE state instead of deleting it altogether.
This seems to break the Join&Leave empty queue functionality.

Does any guru have any ideas?