AI won't have any more fun when the game is over.

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

@@ -695,6 +695,9 @@ public class PhaseHandler extends MyObservable implements java.io.Serializable {
      * </p>
      */
     public final void passPriority() {
+        // stop game if it's outcome is clear
+        if ( game.isGameOver() ) return;
+        
         final Player actingPlayer = this.getPriorityPlayer();
         final Player firstAction = this.getFirstPriority();