Fixes #444 Invalidate UI state/windows when a game starts

Author: behindcurtain3

Pulsar4X/Pulsar4X.Client/Interface/Menus/LoadGame.cs

@@ -48,6 +48,7 @@ internal void LoadFile(string filenamepath)
         string contents = File.ReadAllText(filenamepath);
         var loadedGame = Game.Load(contents);
 
+        _uiState.ClearGameState();
         _uiState.Game = loadedGame;
 
         // TODO: need to figure out a way to properly handle this

Pulsar4X/Pulsar4X.Client/Interface/Menus/NewGameMenu.cs

@@ -528,6 +528,7 @@ void CreateNewGame()
         // Call the game post new game initialization
         game.PostNewGameInitialization();
 
+        _uiState.ClearGameState();
         _uiState.Game = game;
         _uiState.SetFaction(playerFaction, true);
         _uiState.SetActiveSystem(startingSystem.ManagerID);
@@ -746,6 +747,7 @@ public static void QuickstartGame()
             // Initialize game
             game.PostNewGameInitialization();
 
+            _uiState.ClearGameState();
             _uiState.Game = game;
             _uiState.SetFaction(playerFaction, true);
             _uiState.SetActiveSystem(startingSystem.ManagerID);

Pulsar4X/Pulsar4X.Client/State/GlobalUIState.cs

@@ -188,6 +188,27 @@ private void DeactivateAllClosableWindows()
             }
         }
 
+        /// <summary>
+        /// Clears all cached UI state to prepare for a new game.
+        /// This must be called before setting up a new game to prevent stale
+        /// references from the previous game
+        /// </summary>
+        internal void ClearGameState()
+        {
+            LoadedWindows.Clear();
+            LoadedNonUniqueWindows.Clear();
+            EntityWindows.Clear();
+            StarSystemStates.Clear();
+            LastClickedEntity = null;
+            PrimaryEntity = null;
+            Faction = null;
+            PlayerFaction = null;
+            SelectedStarSystemId = "";
+            _lastContextMenuOpenedEntityGuid = -1;
+            ContextMenu = null;
+            ActiveWindow = null;
+        }
+
         internal void SetFaction(Entity factionEntity, bool setAsPlayer = false)
         {
             if(Game == null) throw new NullReferenceException("Game is null");