Moved observer attachment into CStack.java

src/main/java/forge/control/FControl.java

@@ -371,7 +371,6 @@ public enum FControl {
     
         // models shall notify controllers of changes
         
-        game.getStack().addObserver(CStack.SINGLETON_INSTANCE);
         game.getGameLog().addObserver(CLog.SINGLETON_INSTANCE);
         // some observers were set in CMatchUI.initMatch
     

src/main/java/forge/gui/match/controllers/CStack.java

@@ -64,6 +64,8 @@ public enum CStack implements ICDoc, Observer {
     public void setModel(MagicStack model, LobbyPlayer guiPlayer) { 
         this.model = model; 
         this.viewer = guiPlayer;
+        
+        model.addObserver(this);
     }
 
 }