Senna Ult doesn't Damage Baron

While watching the C9 vs FLY game today when C9 was taking the baron towards the end of the game Wild Turtle had a chance to steal the baron for his team. He channeled up the Ult and the Ult went of while the baron was at 150 HP for like 2 seconds. The baron took 0 damage from his ult and it was centered perfectly on top of baron and then C9 eventually got the baron. Riot you need to look into why Senna's Ult doesn't damage the baron. That was rightfully stolen and may or may not have changed the outcome of the game but by not getting the steal it definitely ended the game for C9.