bug when using startls

[junko2013]

XmppWebSocketIo has a bug. When secure is used, the _socket stream has been closed and data can no longer be sent to the server. At this time, calling the write method cannot send it. The solution is to add a new SecureSocket? _secureSocket; object and assign it in the secure method, and then determine whether _secureSocket is empty when writing. If it is not empty, call _secureSocket.write to send data.