fix offline status

wrong exception type catched so IsPortOpen would not return false as expected

WoL/Services/RdpPortPingService.cs

@@ -24,7 +24,7 @@ private static async Task<bool> IsPortOpen(IPAddress ip, int port, TimeSpan time
                 return true;
             }
             catch (Exception ex)
-            when (ex is SocketException || ex is ObjectDisposedException)
+            when (ex is SocketException || ex is OperationCanceledException)
             {
                 return false;
             }