Getting an index from an array pulled from Parse.com - fatal error: Cannot index empty buffer

I'm fairly new to Swift and I've been trying to pull individual items from an array stored in Parse.com

When printing the array itself, I get all the users, however, when attempting to get the first index of an array I get the following error

"fatal error: Cannot index empty buffer"

This is code I'm currently using -

import UIKit
import Parse
class feedTableViewController: UITableViewController {
  var titles = [String]()
  var usernames = [String]()
  var images = [UIImage]()
  var imageFiles = [PFFile]()

  override func viewDidLoad() {
    super.viewDidLoad()
    //....
  }

  override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell {

    var myCell:cell = self.tableView.dequeueReusableCellWithIdentifier("myCell") as cell
    //Error occurs here - does not work due to empty buffer
    myCell.title.text = titles[indexPath.row]
    myCell.username.text = usernames[indexPath.row]
    //If the previous two lines are commented out, I can print out both the arrays
    println(titles)
    println(usernames)

    return myCell
  }
}

Thanks!

Make sure the number of elements in titles matches the number you return in numberOfRowsInSection.