I need some help in Expenses Per Diem Policy

I need some help in Expenses Per Diem Policy

this is my script written for restricting the PerDiem Components. Say if Lodging and Per Day Allowance both is selected from Per Diem Page then the report should gets auto rejected. When Im trying to executing it says the following error {"code":11,"message":"The parameter JSONString is mandatory."}

organizationID = "6XXXXXXXXXXXXXX";
expenseReportID = expense_report.get("report_id");
response = invokeurl
[
url :"https://www.zohoapis.in/expense/v1/expensereports/" + expenseReportID + "?organization_id=" + organizationID
type :GET
connection:"zohoexpenses"
];
//info response;
expense_report_map = response.getJSON("expense_report");
expenses_list = expense_report_map.getJSON("expenses");
flag1 = 0;
for each  expense_rec in expenses_list
{
line_items_list = expense_rec.getJSON("line_items");
for each  rec in line_items_list
{
category_name = rec.getJSON("category_name");
if(category_name == "Lodging")
{
flag1 = 1;
}
if(category_name == "Per Diem Allowance")
{
flag1 = flag1 + 1;
}
}
}
if(flag1 == 2)
{
updateMap = Map();
updateMap.put("status","rejected");
info updateMap;
updateresponse = invokeurl
[
url :"https://www.zohoapis.in/expense/v1/expensereports/" + expenseReportID + "?organization_id=" + organizationID
type :PUT
parameters:updateMap.toString()
connection:"zohoexpenses"
];
info updateresponse;
}