Fix GameState.Close teardown with lock instead of local captures

Local variable captures only prevented NullReferenceException but
not the logical race (double cleanup if two threads call Close
concurrently). Use lock(this) to make the entire teardown atomic.
This is safe because Channel.RemoveUser already locks on the
GameState (reentrant), and no other code path holds a different
lock before calling Close.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: wjlafrance

src/Atlasd/Battlenet/Protocols/Game/GameState.cs

@@ -125,42 +125,41 @@ public static bool CanStatstringUpdate(Product.ProductCode code)
 
         public void Close()
         {
-            // Remove this GameState from ActiveChannel
-            var channel = ActiveChannel;
-            if (channel != null)
+            lock (this)
             {
-                channel.RemoveUser(this); // will change this.ActiveChannel to null.
-            }
+                // Remove this GameState from ActiveChannel
+                if (ActiveChannel != null)
+                {
+                    ActiveChannel.RemoveUser(this); // will change this.ActiveChannel to null.
+                }
 
-            // Notify clan members
-            var clan = ActiveClan;
-            if (clan != null)
-            {
-                clan.WriteStatusChange(this, false); // offline
-            }
+                // Notify clan members
+                if (ActiveClan != null)
+                {
+                    ActiveClan.WriteStatusChange(this, false); // offline
+                }
 
-            // Update keys of ActiveAccount
-            var account = ActiveAccount;
-            if (account != null)
-            {
-                account.Set(Account.LastLogoffKey, DateTime.Now);
+                // Update keys of ActiveAccount
+                if (ActiveAccount != null)
+                {
+                    ActiveAccount.Set(Account.LastLogoffKey, DateTime.Now);
 
-                var timeLogged = (UInt32)account.Get(Account.TimeLoggedKey);
-                var diff = DateTime.Now - ConnectedTimestamp;
-                timeLogged += (UInt32)Math.Round(diff.TotalSeconds);
-                account.Set(Account.TimeLoggedKey, timeLogged);
-            }
+                    var timeLogged = (UInt32)ActiveAccount.Get(Account.TimeLoggedKey);
+                    var diff = DateTime.Now - ConnectedTimestamp;
+                    timeLogged += (UInt32)Math.Round(diff.TotalSeconds);
+                    ActiveAccount.Set(Account.TimeLoggedKey, timeLogged);
+                }
 
-            // Remove this OnlineName from ActiveAccounts and ActiveGameStates
-            if (!string.IsNullOrEmpty(OnlineName))
-            {
-                Battlenet.Common.ActiveAccounts.TryRemove(OnlineName, out _);
-                Battlenet.Common.ActiveGameStates.TryRemove(OnlineName, out _);
-            }
+                // Remove this OnlineName from ActiveAccounts and ActiveGameStates
+                if (!string.IsNullOrEmpty(OnlineName))
+                {
+                    Battlenet.Common.ActiveAccounts.TryRemove(OnlineName, out _);
+                    Battlenet.Common.ActiveGameStates.TryRemove(OnlineName, out _);
+                }
 
-            // Remove this GameAd
-            var gameAd = GameAd;
-            if (gameAd != null && gameAd.RemoveClient(this)) GameAd = null;
+                // Remove this GameAd
+                if (GameAd != null && GameAd.RemoveClient(this)) GameAd = null;
+            }
         }
 
         public void Dispose() /* part of IDisposable */