How to use psi-archery?

[forceedge]

With a telekinetic-wield bow and arrow(not ammo!) equipped,and no weapon in hand, i casted master telekinetic archery, then the arrow just disappear.Message log said youmust equipped a ammo(arrow?) to use the talent

Then i buy more arrow and tried a few times the arrow just diasppear and gone forever...

Is it a bug or i just didnt do it correctly?

btw, version b38