Parentwindow reference error

Parentwindow reference error

Hi,
I have a use case where I would like to embed an iframe in the Zohodesk layout and open our application from inside the iframe. Using this iframe I can do various operations using Zoho Desk API.So, I created the extension using Zoho Desk Extension documentation and was able to open my application within the iframe. See the image below for more clarity.
                                                
Now I want the contacts from the Zoho Desk portal through Zoho API('https://desk.zoho.com/api/v1/contacts')  within my 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 app but cannot get the response of the contact API and get the parent window reference error. However, the API gives the response when it is called from the widget.html file this problem only occurs when I called the API from the iframe and I only need this contact in my app not in the extension.
            



I did the following step. 
  1. create extension.
  2. Load my application in an iframe.
  3. upload extension.
In case you are wondering why I want to open my app in an iframe because we are looking for API CTI integration to connect our Cloud-based Call application to Zohodesk.
I have uploaded the extension code below in case you want to check. 

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