Error when tile container gets called

Hi,

I have the following scenario

1. When user logins landing page, user can able to navigate between tiles

2. To go back to the landing page, when user click on Back button on the header (green colour button), I am getting the following error

Details of the error

On click of the button the following code get called

onBackButtonPress:function(oEvent,oData){

// window.location = util.getServiceUrl(CONSTANTS.APPLOCATION);

var sViewToNavTo = "landingPage";

var bus = sap.ui.getCore().getEventBus();

bus.publish("nav", "to", {

id : sViewToNavTo,

data : {}

});

  },

The landing page has a tile container which adds the tiles.

Can you help is highly appreciated