Ionic Analytics: can't post events

When I turn on the ionic analytics by following the step-by-step guide:

and then turn on auto tracking using the ion-auto-track attribute. When I run the app I see the following error messages from the console:

POST http://localhost:8100/undefined/api/v1/events/e8918706 404 (Not Found).

By going through the code, i.e, www/ionic-analytics.js, I see that

getApiServer: function() {
return $ionicApp.getValue(‘analytics_api_server’);
},

this method is returning “undefined”. I did not see any documentation about specifying the “analytics_api_server” parameter. It is not clear from the documentation where the data is going to be sent and how to retrieve the data.

thanks for your help!
Ming