Script Error: Could not parse the body as Plain-Text. (Content-Type=text/html; charset=utf-8)

Proxyman version? (Ex. Proxyman 1.4.3)

Version 2.30.0

macOS Version? (Ex. mac 10.14)

11.4

Steps to reproduce

function onResponse(context, url, request, response) {
var bodyStr = response.body;
var decodeBody = atob(bodyStr);
var jsonBody = JSON.parse(decodeBody);
var counter = jsonBody["count"];
counter = counter + 1;
console.log(counter);
var jsonBody["count"] = counter;
var jsonStr= JSON.stringify(jsonBody);
var jsonEncode = btoa(jsonStr);
console.log(jsonEncode);
response.body = jsonEncode;
return response;
}

Expected behavior

In the last step, it should base64 encode the json string and send it to the client, but the log shows null for json.Encode and throws the following error:
❌Error: Could not parse the body as Plain-Text. (Content-Type=text/html; charset=utf-8)

Screenshots (optional)