Getting error when upserting data extension with SSJS

I am trying to query the contact and another data extension and then upsert a third data extension called customerETL.

Everything works if I hardcode values into the function but when I pass values through a for loop, I get the following error:

{"message":"Length cannot be less than zero.\r\nParameter name: length","description":"System.ArgumentOutOfRangeException: Length cannot be less than zero.\r\nParameter name: length – from Jint\r\n\r\n"}

Here is the code:

<script runat="server" language="JavaScript">
Platform.Load("core", "1.1.1");

    function getPreferences(subkey, email, deName, fieldname){
        var dataExt = DataExtension.Init(deName);
        var dataFilter = {Property:"Subscriberkey",SimpleOperator:"equals",Value:subkey};
        var data = dataExt.Rows.Retrieve(dataFilter);
    
        data = data[0]
    
        var dataConcatList = "";
    
        var dataTrueFields = [];
    
        for (var key in data){
            if(data[key] === "True"){
                dataTrueFields.push(key);
            }
        }
    
        for (var i = 0; i < dataTrueFields.length; i++) {
            dataConcatList += dataTrueFields[i] + "|";
        }
    
        var result = dataConcatList.slice(0, -1);
        var attribute = Stringify(result);
        attribute = attribute.replace(/"/g, '');

    
        var deName = "customerETL"; 
        whereColumnArr = ["attribute:sfmcContactKey","attribute:emailAddress"];
        whereColumValueArr = [subkey, email]; 
        upsertColumnArr = [fieldname]; 
        upsertColumnValueArr = [attribute];

        var upsertedRowCount = Platform.Function.UpsertDE(
            deName,
            whereColumnArr,
            whereColumValueArr,
            upsertColumnArr,
            upsertColumnValueArr
        );
    }
    
try {

    var contactDE = DataExtension.Init("Contact");
    var contactData = contactDE.Rows.Retrieve();
    
    var listOfsubkeys = [];
    var listOfemails = [];
    
    for (var n = 0; n < contactData.length; n++){
        listOfsubkeys.push(contactData[n]["Subscriberkey"]);
        listOfemails.push(contactData[n]["EmailAddress"]);
    }
    
    for (var i = 0; i < contactData.length; i++){
        getPreferences(listOfsubkeys[i],listOfemails[i],"travel_reasons","attribute:reasons")
    }
}
catch (error){
    var err = Stringify(error);
    Write(err);
} 
    

    

</script>

Thanks in advance.