Parentwindow reference error

Parentwindow reference error

Hello,
As we cannot directly upload our extension to the Zoho desk. Firstly, we have to make a node app and upload the zip file. So, I load my third-party application in an iframe within the widget.html file. 
Now I want the contacts from the Zoho Desk portal through Zoho API('https://desk.zoho.com/api/v1/contacts') 
within my third-party application which is currently loaded in an iframe. So, the issue I am facing is that  I get the instance of the Zoho desk within my third-party app but cannot get the response of the contact API and get the parentWindow reference error.
Please guide me through the process of how can I resolve this error.













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