Fix flashback zone to work more like other zones and not crash for desktop game

forge-game/src/main/java/forge/game/card/CardView.java

@@ -335,6 +335,7 @@ public class CardView extends GameEntityView {
         case Exile:
         case Battlefield:
         case Graveyard:
+        case Flashback:
         case Stack:
             //cards in these zones are visible to all
             return true;

forge-game/src/main/java/forge/game/player/Player.java

@@ -1146,6 +1146,9 @@ public class Player extends GameEntity implements Comparable<Player> {
             }
             return cards;
         }
+        else if (zoneType == ZoneType.Flashback) {
+            return getCardsActivableInExternalZones(true);
+        }
 
         PlayerZone zone = getZone(zoneType);
         return zone == null ? CardCollection.EMPTY : zone.getCards(filterOutPhasedOut);

forge-game/src/main/java/forge/game/player/PlayerView.java

@@ -223,6 +223,8 @@ public class PlayerView extends GameEntityView {
             return TrackableProperty.Hand;
         case Library:
             return TrackableProperty.Library;
+        case Flashback:
+            return TrackableProperty.Flashback;
         default:
             return null; //other zones not represented
         }
@@ -231,6 +233,17 @@ public class PlayerView extends GameEntityView {
         TrackableProperty prop = getZoneProp(zone.getZoneType());
         if (prop == null) { return; }
         set(prop, CardView.getCollection(zone.getCards()));
+
+        //update flashback zone when graveyard, library, or exile zones updated
+        switch (zone.getZoneType()) {
+        case Graveyard:
+        case Library:
+        case Exile:
+            set(TrackableProperty.Flashback, CardView.getCollection(zone.getPlayer().getCardsIn(ZoneType.Flashback)));
+            break;
+        default:
+            break;
+        }
     }
 
     public int getMana(final byte color) {

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

@@ -13,6 +13,7 @@ public enum ZoneType {
     Graveyard(false),
     Battlefield(false),
     Exile(false),
+    Flashback(false),
     Command(false),
     Stack(false),
     Sideboard(true),