Taste of Vitae for Zero

My search skills have failed me. I recall being told that you can't Taste of Vitae for zero. I didn't question it at the time, but I can't find any evidence for this in the rules.

In this scenario, a player simply wants to cycle ToV at the end of the round when the opposing vampire lost no blood to damage during the round.

Taste of Vitae
Only usable at the end of a round of combat. Not usable by a vampire being burned or going to torpor. A vampire can play only one Taste of Vitae each round. This vampire gains blood equal to the amount of blood lost by the opposing vampire to damage this round.

Thanks!

You can taste for zero from a vampire.

You cannot taste from an ally.

Thank you, Cordovader!

As Cordo said, you can taste for zero. Even if opponent played a combat end.

another subtlety, if you play catatonic fear and than taste of vitae, you still don't get any blood, as the damage is done after the combat ends.