[Modify] Polish it

websocket-sharp/Server/WebSocketServiceManager.cs

@@ -289,10 +289,13 @@ namespace WebSocketSharp.Server
     private void broadcast (Opcode opcode, Stream stream, Action completed)
     {
       var cache = new Dictionary<CompressionMethod, Stream> ();
+
       try {
         foreach (var host in Hosts) {
-          if (_state != ServerState.Start)
+          if (_state != ServerState.Start) {
+            _log.Error ("The server is shutting down.");
             break;
+          }
 
           host.Sessions.Broadcast (opcode, stream, cache);
         }