[GAMEPLAY] Vi became unstoppable for 7 seconds

During Vi's ult her target died to an invisible Ezreal's ultimate and it made her unstoppable for 7 seconds afterwards. I don't know why it occurred but to summarize what happened in points ​1. Vi started ult animation locking Kayn. 2. Kayn died to Ezreal's ult which was invisible since it's launching. 3. Kayn died during vi's ultimate animation. 4. Vi became unstoppable for 7 seconds afterwards.