Kind of a strange exception here. Ice Blast is able to debuff invulnerable units

Repro:
1. Buy Eul's Scepter
2. See Ice Blast coming in
3. Cyclone yourself in attempt to dodge the Ice Blast

Result: The impact damage is dodged, obviously, due to the invulnerability. But it still places its debuff on you.

Expected: Ice Blast shouldn't place its debuff on invulnerable units.