[GAMEPLAY] Warwick Q Bug

We all know Warwick Q follows any sort of mobility, what you will see here at the end of the clip is Warwick following the Lissandra E. The curious thing that happens though is because Lissandra dies mid-casting the second part of her E, Warwick teleports back and forth for some reason. The question is, when did Lissandra die, and what is the meaning of this visual bug.