Aatrox Glacial Bug

Aatrox's spell is canceled by glacial. If Aatrox begins to cast his spell, and he is frozen (glacial proc) mid-animation (in the air, about to bring his sword down), the spell doesn't finish casting and he loses all his mana. Is this intentional? Doesn't seem like it bc it's a MASSIVE counter/damage loss. Happened 3-4 times to me in a single game (had Aatrox in the front against a heavy glacial comp) and definitely lost some of those battles because of it.