Ensure undo stack cleared when phase changes

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

@@ -183,6 +183,8 @@ public class PhaseHandler implements java.io.Serializable {
             }
         }
 
+        game.getStack().clearUndoStack(); //can't undo action from previous phase
+
         String phaseType = oldPhase == phase ? "Repeat" : phase == PhaseType.getNext(oldPhase) ? "" : "Additional";
 
         if (this.phase == PhaseType.UNTAP) {

forge-game/src/main/java/forge/game/zone/MagicStack.java

@@ -256,6 +256,15 @@ public class MagicStack /* extends MyObservable */ implements Iterable<SpellAbil
         return true;
     }
 
+    /**
+     * <p>
+     * clearUndoStack.
+     * </p>
+     */
+    public final void clearUndoStack() {
+        undoStack.clear();
+    }
+
     /**
      * <p>
      * add.