Unable to extract image URL from an amazon product page using Webview flutter package

Question

I am using the below function in Flutter (package: webview_flutter) to extract a specific image of a product from Amazon website. But I am getting null value

Below is my function. It returns correct values when I give 'document.cookie' and 'document.location.href' in the runJavaScriptReturningResult function. But when I give a complex path, it's unable to get the value of the image url.

Future<void> _onGetFocusImage(WebViewController controller) async {
  final focusImage = await controller
   .runJavaScriptReturningResult('document.getElementById("unrolledImgNo0").querySelector("img").getAttribute("src")');
  if (!mounted) return;
  ScaffoldMessenger.of(context).showSnackBar(
    SnackBar(
      content: Text('$focusImage'),
    ),
  );
  print("url is $focusImage");
}

I don't believe that the parameter to below library function is a problem. As I checked that argument is definitely string type. Where am I going wrong? Please suggest why for certain document attributes I am getting the value when I call below function but for other document attributes I am not getting any value

 Future<Object> runJavaScriptReturningResult(String javaScript) {
    return platform.runJavaScriptReturningResult(javaScript);
  }

You can for any product URL. But i checked for below link

https://www.amazon.in/dp/B07XKCXPNN/ref=sspa_dk_detail_7?psc=1&pd_rd_i=B07XKCXPNN&pd_rd_w=xfA7J&content-id=amzn1.sym.0fcdb56a-738b-4621-9da7-d47193883987&pf_rd_p=0fcdb56a-738b-4621-9da7-d47193883987&pf_rd_r=BEJ1AGY5NZDQHAP376T3&pd_rd_wg=BZo9B&pd_rd_r=f3666f20-3db5-486c-aac2-cc6abcb2561d&s=apparel&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWwy