- Prevent NPE in getDefenderByAttacker.

src/main/java/forge/Card.java

@@ -6654,10 +6654,11 @@ public class Card extends GameEntity implements Comparable<Card> {
      */
     public final boolean isAttacking(GameEntity ge) {
         Combat combat = getGame().getCombat();
-        if (!combat.isAttacking(this)) {
+        GameEntity defender = combat.getDefenderByAttacker(this);
+        if (!combat.isAttacking(this) || defender == null) {
             return false;
         }
-        return combat.getDefenderByAttacker(this).equals(ge);
+        return defender.equals(ge);
     }
 
     /**

src/main/java/forge/game/phase/Combat.java

@@ -272,6 +272,9 @@ public class Combat {
      * @return a {@link java.lang.Object} object.
      */
     public final GameEntity getDefenderByAttacker(final Card c) {
+        if (!this.attackerToBandMap.containsKey(c)) {
+            return null;
+        }
         return this.attackerToBandMap.get(c).getDefender();
     }