Index Out of range Swift - swift

Question

I occasionally get an error 'Index out of Range' from the following code:
I suspect its to do with the way the table data is reloaded and have tried moving it in and out of the loop but no avail.
any help resolving this would be much appreciated!
override func viewDidAppear(_ animated: Bool) {
self.tableView.rowHeight = 150
self.tableData.removeAll(keepingCapacity: true)
self.tableImages.removeAll(keepingCapacity: true)
self.tableDesc.removeAll(keepingCapacity: true)
// Register custom cell
let nib = UINib(nibName: "vwTblCell", bundle: nil)
tableView.register(nib, forCellReuseIdentifier: "cell")
let url = NSURL(string: "https://www.checkmyweave.co.uk/backend/offerstest.php")!
let task = URLSession.shared.dataTask(with: url as URL) { (data, response, error) -> Void in
if let urlContent = data {
do {
if let jsonResult = try JSONSerialization.jsonObject(with: urlContent, options: []) as? [[String:AnyObject]] {
var i = 0
while i < jsonResult.count {
self.tableData.append(jsonResult[i]["offertitle"]! as! String)
self.tableImages.append(jsonResult[i]["imagename"]! as! String)
self.tableDesc.append(jsonResult[i]["offerdesc"]! as! String)
i = i + 1
}
}
} catch {
print("JSON serialization failed")
}
} else {
print("ERROR FOUND HERE")
}
DispatchQueue.main.async(execute: { () -> Void in
self.tableView.reloadData()
})
}
task.resume()
}