TypeError: Cannot read property 'sockets' of undefined with nodejs

I can start node app.js config.file just fine
but it soon ends with this error:

[2016/06/19 03:02:48] authenticateClientCallback: Valid login for uid 1
[2016/06/19 03:02:48] sendPresenceChangeNotification: onlineUsers
{ '1': [] }
Auth - 1
/usr/lib/node_modules/drupal-node.js/lib/client-manager.js:806
if (this.sockets[sessionId]) {
^

TypeError: Cannot read property 'sockets' of undefined
at ClientManager.publishMessageToClient (/usr/lib/node_modules/drupal-node.js/lib/client-manager.js:806:11)
at process. (/usr/lib/node_modules/drupal-node.js/extensions/drupalchat_nodejs.server.extension.js:26:7)
at emitTwo (events.js:87:13)
at process.emit (events.js:172:7)
at ClientManager.setupClientConnection (/usr/lib/node_modules/drupal-node.js/lib/client-manager.js:260:11)
at ClientManager.authenticateClientCallback (/usr/lib/node_modules/drupal-node.js/lib/client-manager.js:215:8)
at Request._callback (/usr/lib/node_modules/drupal-node.js/lib/client-manager.js:90:28)
at Request.self.callback (/usr/lib/node_modules/drupal-node.js/node_modules/request/request.js:198:22)
at emitTwo (events.js:87:13)
at Request.emit (events.js:172:7)