web登出报错WebSocket connection to 'wss://im-api.easemob.com/ws/' failed: Data frame received after clos

使用web-IM按照demo，登出时提示：WebSocket connection to 'wss://im-api.easemob.com/ws/' failed: Close received after close
登出代码：

                conn.close('logout');

                conn.errorType = WebIM.statusCode.WEBIM_CONNCTION_CLIENT_LOGOUT;

版本：websdk-1.4.13.js, strophe-1.2.8.min.js,