Ionic 3 Contentwindow is Null Error

Appflow
1

I am having problem during navigating back to home page ,it says contentwindow is null of iframe.
Plz someone help me in resolving that.

Home.ts file:
var widget = document.getElementById(“widget”)[‘contentWindow’];

        widget.postMessage({
            'run': 'setClass',
            'class': this.deck + ' ' + this.activeOpeningName,
        }, '*')