508.4a

If the effect that puts a creature onto the battlefield attacking specifies it’s attacking a certain player, and that player is no longer in the game when the effect resolves, the creature is put onto the battlefield but is never considered an attacking creature. The same is true if the effect specifies a creature is put onto the battlefield attacking a planeswalker or battle and, when the effect resolves, that permanent is no longer on the battlefield, is no longer a planeswalker or battle, is a planeswalker that is no longer controlled by a defending player, or is a battle that is no longer protected by a defending player.