Attacking you abilities and filters - fixed that planeswalker removes from a combat can cause a game error (NPE error, example: Curse of Hospitality)

Mage/src/main/java/mage/game/combat/CombatGroup.java

@@ -31,7 +31,7 @@ public class CombatGroup implements Serializable, Copyable<CombatGroup> {
     protected List<UUID> attackerOrder = new ArrayList<>();
     protected Map<UUID, UUID> players = new HashMap<>();
     protected boolean blocked;
-    protected UUID defenderId; // planeswalker or player
+    protected UUID defenderId; // planeswalker or player, can be null after remove from combat (e.g. due damage)
     protected UUID defendingPlayerId;
     protected boolean defenderIsPermanent;