use subscribe instead of assign.

src/Avalonia.X11/X11TrayIconImpl.cs

@@ -85,10 +85,7 @@ namespace Avalonia.X11
             _statusNotifierItemDbusObj.SetTitleAndTooltip(_tooltipText);
             _statusNotifierItemDbusObj.SetIcon(_icon);
 
-            _statusNotifierItemDbusObj.ActivationDelegate = () =>
+            _statusNotifierItemDbusObj.ActivationDelegate += OnClicked;
-            {
-                OnClicked?.Invoke();
-            };
 
             _isActive = true;
         }