Rule 508.4a

If a creature would be put onto the battlefield attacking a certain player, and that player is no longer in the game, the creature is put onto the battlefield but is never considered an attacking creature. The same is true if a creature would be put onto the battlefield attacking a planeswalker or battle and 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.