Removing 'undefined' from output before writing to Google Sheets - google-apps-script

Question

My script below returns 'undefined' to the Google Sheet when I add dfStatus.error.count to the array to be written.
function getDatafeedStatus() {
var d = new Date();
var ar = [];
for (var a in FEEDS) {
for (var i = 0; i < FEEDS[a].length; i++) {
try {
var dfStatus = ShoppingContent.Datafeedstatuses.get(a, FEEDS[a][i]);
// see https://developers.google.com/shopping-content/v2/reference/v2/datafeedstatuses for detail on this API call
ar.push([d, a, FEEDS[a][i], dfStatus.processingStatus, dfStatus.lastUploadDate, dfStatus.itemsValid, dfStatus.errors.count]);
} catch (e) {
Logger.log(e.message); // check View > Logs after running the script if a feed does not appear to be fetching correctly
}
}
}
appendArrayToSheet(ar, 'status');
}
/**
* Add an array to the bottom of a sheet. If the sheet doesn't exist, it is created.
* #param {array} ar - the array to write
* #param {string} sheetName - the name of the sheet to which to write
*/
function appendArrayToSheet(ar, sheetName){
if (ar.length !== 0 && ar[0].length !== 0){
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getSheetByName(sheetName);
if (sheet == null) {
sheet = ss.insertSheet();
sheet.setName(sheetName);
};
var range = sheet.getDataRange();
var row = range.getLastRow() + 1;
var newRange = sheet.getRange(row, 1, ar.length, ar[0].length);
newRange.setValues(ar);
}
Any ideas whats wrong with it? I must say I'm not a JavaScript expert. I'm trying modify the code which is already used somewhere else.