Ripple - Uncaught Error: Load timeout for modules: app http://requirejs.org/docs/errors.html#timeout

I am using jQuery, backbone.js, underscore.js and Bootstrap 3 for my mobile app project. I'm running my app in Ripple. Sometimes I get this silly error in my console.

Uncaught Error: Load timeout for modules: app
http://requirejs.org/docs/errors.html#timeout 

Why does it happen?

I have set require js config option waitSeconds to 0 and the error was gone.

My Configuration:

require.config({

  baseUrl: 'app/lib',

  paths: {
    app: '../js',
    tpl: '../tpl'
  },
  urlArgs: "bust=" +  (new Date()).getTime(),
  waitSeconds: 0,
  shim: {
    'zepto': {
        exports: '$'
    },

    'backbone': {
        //These script dependencies should be loaded before loading
        //backbone.js
        deps: ['zepto', 'underscore'],
        //Once loaded, use the global 'Backbone' as the
        //module value.
        exports: 'Backbone'
    },
    'underscore': {
        exports: '_'
    }
  }  

});

hope this help