Netplay: Fixed a couple of crashes and the "select controller" menu

-A client disconnecting could cause the server to crash
-A server stopping, then starting again, could cause the client to crash when reconnecting to the server after getting disconnected by the server stopped
-The select controller menu was not getting updated and was always empty

Core/Netplay/GameClient.cpp

@@ -25,6 +25,8 @@ bool GameClient::Connected()
 
 void GameClient::Connect(ClientConnectionData &connectionData)
 {
+	Disconnect();
+
 	_stop = false;
 	unique_ptr<Socket> socket(new Socket());
 	if(socket->Connect(connectionData.Host.c_str(), connectionData.Port)) {

Core/Netplay/GameServer.cpp

@@ -45,6 +45,8 @@ void GameServer::UpdateConnections()
 	vector<unique_ptr<GameServerConnection>> connectionsToRemove;
 	for(int i = (int)_openConnections.size() - 1; i >= 0; i--) {
 		if(_openConnections[i]->ConnectionError()) {
+			//Pause emu thread to ensure nothing else modifies/accesses the _openConnections list while removing dead connections
+			auto lock = _emu->AcquireLock();
 			_openConnections.erase(_openConnections.begin() + i);
 		} else {
 			_openConnections[i]->ProcessMessages();

UI/ViewModels/MainMenuViewModel.cs

@@ -1246,10 +1246,10 @@ private async void InstallHdPack(Window wnd)
 			}
 		}
 
-		public void UpdateNetplayMenu()
+		public bool UpdateNetplayMenu()
 		{
 			if(!NetplayApi.IsServerRunning() && !NetplayApi.IsConnected()) {
-				return;
+				return false;
 			}
 
 			List<object> controllerActions = new();
@@ -1276,7 +1276,9 @@ public void UpdateNetplayMenu()
 				playerIndex++;
 			}
 
-			controllerActions.Add(new ContextMenuSeparator());
+			if(controllerActions.Count > 0) {
+				controllerActions.Add(new ContextMenuSeparator());
+			}
 
 			controllerActions.Add(new MainMenuAction() {
 				ActionType = ActionType.Custom,
@@ -1286,6 +1288,8 @@ public void UpdateNetplayMenu()
 			});
 
 			_selectControllerAction.SubActions = controllerActions;
+
+			return true;
 		}
 	}
 }

UI/Views/MainMenuView.axaml.cs

@@ -3,6 +3,7 @@
 using Avalonia.Markup.Xaml;
 using Mesen.Utilities;
 using Mesen.ViewModels;
+using System.Collections;
 
 namespace Mesen.Views
 {
@@ -31,7 +32,13 @@ private void InitializeComponent()
 		private void mnuTools_Opened(object sender, RoutedEventArgs e)
 		{
 			if(DataContext is MainMenuViewModel model) {
-				model.UpdateNetplayMenu();
+				if(model.UpdateNetplayMenu() && e.Source is MenuItem item) {
+					//Force a refresh of the tools menu to ensure
+					//the "Select controller" submenu gets updated
+					IEnumerable? items = item.ItemsSource;
+					item.ItemsSource = null;
+					item.ItemsSource = items;
+				}
 			}
 		}
 	}