Fix some warnings

DesktopNotifications.Apple/AppleNotificationManager.cs

@@ -2,6 +2,8 @@
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 
+#pragma warning disable 0067
+
 namespace DesktopNotifications.Apple
 {
     public class AppleNotificationManager : INotificationManager

DesktopNotifications.Windows/WindowsNotificationManager.cs

@@ -90,7 +90,7 @@ namespace DesktopNotifications.Windows
 
             //TODO: Lookup notification object from history?
             _notificationActivatedHandler.Invoke(this,
-                new NotificationActivatedEventArgs(null, _launchAction));
+                new NotificationActivatedEventArgs(null!, _launchAction));
 
             _launchAction = null;
         }