How to use Pointer relations from Parse in TableViews?

I basically have a ViewController which shows a few different categories (solved that with a PFQueryTableViewController). Depending on which Cell I tap a segue to the next ViewController is performed, where all objects, which belong to the tapped Category, should appear.

What I did:

I have 2 classes in parse. The class which shows the objects in a Category (the Questions) has a pointer-column to the Category class (filled that pointer-column with the objectIDs from the Category class objects, is that correct?)

In my firstVC: Here I fill my TableView with the categories (works)

class ChooseCategoriesVC: PFQueryTableViewController {

var textOfSelectedCell:String = ""

// Initialise the PFQueryTable tableview
override init!(style: UITableViewStyle, className: String!) {
    super.init(style: style, className: className)
}

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)

    // Configure the PFQueryTableView
    self.parseClassName = "Category"
    self.textKey = "categoryName"
    self.pullToRefreshEnabled = true
    self.paginationEnabled = false
}

    // Define the query that will provide the data for the table view
    override func queryForTable() -> PFQuery! {
    var query = PFQuery(className: "Category")
    query.orderByAscending("categoryName")
    query.whereKey("active", equalTo: true)
    return query
}

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

    override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: PFObject) -> PFTableViewCell {

    var Cell = tableView.dequeueReusableCellWithIdentifier("Cell") as CustomChooseCategoriesCell!
    if Cell == nil {
        Cell = CustomChooseCategoriesCell(style: UITableViewCellStyle.Default, reuseIdentifier: "Cell")
    }

    // Extract values from the PFObject to display in the table cell
    Cell.chooseCategoryLabel.text = object["categoryName"] as String!

    var thumbnail = object["categoryIcon"] as PFFile
    var initialThumbnail = UIImage(named: "categoryIcon")
    Cell.customChooseCategoryIcon.image = initialThumbnail
    Cell.customChooseCategoryIcon.file = thumbnail
    Cell.customChooseCategoryIcon.loadInBackground()

    return Cell
}

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {

    //get text of selected Cell
    let indexPath = tableView.indexPathForSelectedRow()!
    let selectedCell = tableView.cellForRowAtIndexPath(indexPath) as CustomChooseCategoriesCell!
    textOfSelectedCell = selectedCell.chooseCategoryLabel.text!
    self.performSegueWithIdentifier("vcToChooseQuestion", sender: self)
}

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    //Pass ObjectId of selected Category from ChooseCategoryVC to ChooseQuestionVC
    var detailVC : ChooseQuestionVC = segue.destinationViewController as ChooseQuestionVC
    detailVC.selectedCategoryText = textOfSelectedCell
    }
}

In my secondVC: I need all detailObjects (Questions) to my category

class ChooseQuestionVC: PFQueryTableViewController{

var selectedCategoryText : String!
let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate

// Initialise the PFQueryTable tableview
override init!(style: UITableViewStyle, className: String!) {
    super.init(style: style, className: className)
}

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)

    // Configure the PFQueryTableView
    self.parseClassName = "Question"
    self.textKey = "question"
    self.pullToRefreshEnabled = true
    self.paginationEnabled = false
}

// Define the query that will provide the data for the table view
override func queryForTable() -> PFQuery! {
    var query = PFQuery(className: "Question")
    query.whereKey("column", equalTo: self.appDelegate.getParseData(selectedCategoryText))
    query.orderByAscending("question")
    return query
}

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

override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath, object: PFObject) -> PFTableViewCell {

    var Cell = tableView.dequeueReusableCellWithIdentifier("Cell") as CustomChooseQuestionCell!
    if Cell == nil {
        Cell = CustomChooseQuestionCell(style: UITableViewCellStyle.Default, reuseIdentifier: "Cell")
    }

    // Extract values from the PFObject to display in the table cell
    Cell.chooseQuestionLabel.text = object["question"] as String!

    return Cell
}

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    performSegueWithIdentifier("nextVC", sender: self)
    }
}

My function in AppDelegate:

func getParseData(textOfSelectedCell: String) -> PFObject{

    var query2 = PFQuery(className:"Category")
    query2.whereKey("categoryName", equalTo: textOfSelectedCell)
    query2.findObjectsInBackgroundWithBlock {
        (objects: [AnyObject]!, error: NSError!) -> Void in
        if error == nil {
            // The find succeeded.
            println("Successfully retrieved \(objects.count) scores.")
            // Do something with the found objects
            if let objects = objects as? [PFObject] {
                for object in objects {
                    self.selectedObject = object
                }
            }
        }
        else {
            // Log details of the failure
            println("Error: \(error) \(error.userInfo!)")
        }
    }
    println(selectedObject)
    return selectedObject!

When running the code like this I always get the error

fatal error: unexpectedly found nil while unwrapping an Optional value

How can I solve that?