Fix crash when linux tray icon's visibility is toggled on/off. (#15582)

* Call RemoveMethodHandlers to "dispose" method handlers in dbus tray icons.

* just move the handler to the ctor and remove the reflection hacks

src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs

@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Reflection;
 using System.Threading.Tasks;
 using Avalonia.Controls.Platform;
 using Avalonia.Logging;
@@ -52,7 +54,10 @@ namespace Avalonia.FreeDesktop
             _dbusMenuPath = DBusMenuExporter.GenerateDBusMenuObjPath;
 
             MenuExporter = DBusMenuExporter.TryCreateDetachedNativeMenu(_dbusMenuPath, _connection);
-
+           
+            _statusNotifierItemDbusObj = new StatusNotifierItemDbusObj(_connection, _dbusMenuPath);
+            _connection.AddMethodHandler(_statusNotifierItemDbusObj);
+            
             WatchAsync();
         }
 
@@ -107,9 +112,6 @@ namespace Avalonia.FreeDesktop
             var tid = s_trayIconInstanceId++;
 
             _sysTrayServiceName = FormattableString.Invariant($"org.kde.StatusNotifierItem-{pid}-{tid}");
-            _statusNotifierItemDbusObj = new StatusNotifierItemDbusObj(_connection, _dbusMenuPath);
-
-            _connection.AddMethodHandler(_statusNotifierItemDbusObj);
             await _dBus!.RequestNameAsync(_sysTrayServiceName, 0);
             await _statusNotifierWatcher.RegisterStatusNotifierItemAsync(_sysTrayServiceName);