Should convert reponse[1] to byte[] instead of String in handleMessage.

line 189:
sendFailureMessage(e, (byte[]) null);

line 150:
handleFailureMessage((Throwable)response[0], (byte[]) response[1]);
in some situation, response[1] can be null, so that response[1].toString() will throw exception.

furthormore, convert reponse[1] to String will let AsyncHttpResponseHandler::handleFailureMessage be invoked instead of BinaryHttpResponseHandler::handleFailureMessage.