[Fix] Handle it

websocket-sharp/Net/HttpListenerAsyncResult.cs

@@ -179,11 +179,17 @@ namespace WebSocketSharp.Net
 
     internal void Complete (HttpListenerContext context, bool syncCompleted)
     {
+      try {
         var lsnr = context.Listener;
         if (!lsnr.Authenticate (context)) {
           lsnr.BeginGetContext (this);
           return;
         }
+      }
+      catch (Exception ex) {
+        Complete (ex);
+        return;
+      }
 
       _context = context;
       _syncCompleted = syncCompleted;