[Gameplay] Lux ult failing to do damage during a knockup

In my recent games with lux, on both EUW and NA servers, I have noticed that using a knockup* will cause Lux' ult to fire, and go on a full cooldown, without doing any damage. This appears to be a bug, not an intended feature, based on how Lux' ult behaves when she dies, as well as other forms of crowd control don't seem to have the same effect.

This shouldn't be too hard to reproduce, step 1, level a lux to level 6, step 2, put down a ziggs satchel, step 3, have lux ult, step 4, detonate the knockup while Lux is casting, so that she is in the air when the ult finishes casting**

I don't have videos that show this yet, I will try to make one later when I have time. *the knockups in question were Poppy's ultimate and Ziggs' Satchel. **I don't know if this is a requirement, but it happened both times. Poppy's ultimate would most likely be the easiest skill to reproduce this bug with due to the length of her knockup