Leona Q disappearing

I just played 2 games with Leona on EUW and encountered a bug. When trying to kill a target with Leona's Q activated, the spell will go on cooldown even when the target died before you could hit it. It was 10/10 reproducable.

1. Activate Q
2. Try hitting a target that is about to die -->It dies before your animation finished
3. Q goes on cooldown without having hit anything.

EDIT: The same bug got reported 2 months ago but since it's still not fixed I wanted to post it again.