Warwick GAMEPLAY bug

I have been playing this game since s7 , thats when warwick got reworked and since then his Q ability has this bug when you Q a target after he dies it still goes off, you q nothing and you heal from nothing and you use your mana for no reason and this bug works on every target (minions , monsters and champs ) and this affect the gameplay of the champ because his q is a big part of his kit , and after his buff you have to max it first and then you use it for nothing .