Issues getting data from plist with nested dictionaries

Hi, I'm a real newbie and have got stuck with issues reading data from a plist ("Questions") i constructed for a Master-Detail Quiz app. The root class and subclasses for the plist are NSDictionary, where keys list the question number and values the text as String. The plist is structured as follows: Current questions(root) with three subcategories: SubjectAreas + SubQuestions + QuestionStems. The app crashes as when loading optional it finds nil in the part of the code (see below) that attempts to assign a String from the struct to a UILabel (QuestionStemLabel). Also, I wondered what the best way to indicate True/False for each and every subquestion is. It looks like swift loads Bool data from the dictionary as Int. In advance thanks for any and all advice!

// Struct to organize the questions, subject areas etc. ///

struct questions { let questionSubject: String? let questionStem: String? let subQuestion: String?

init(questionDictionary: [String: AnyObject]) {
    questionSubject = questionDictionary["SubjectAreas"] as? String
    questionStem = questionDictionary["QuestionStems"] as? String
    subQuestion = questionDictionary["Subquestions"] as? String

}

}

////////////////////////DetailViewController///////////////

var stemLabel: AnyObject? {
    didSet {
        // Update the view.
        self.configureView()
    }
}

func configureView() {

// Loading the property list////

    if let plistPath = NSBundle.mainBundle().pathForResource("Questions", ofType: "plist"),
        let questionDictionary = NSDictionary(contentsOfFile: plistPath),
        let currentQuestionDictionary = questionDictionary["CurrentQuestions"] as? [String: AnyObject]
    {

        println(currentQuestionDictionary) /// This prints the dictionary, so it has imported

        let currentQuestion = questions(questionDictionary: currentQuestionDictionary)

    }

///// The app crashed when I tried configure view and labels, as optional returned nil ///

    if let stem: AnyObject = self.questionStem {
        if let label = self.QuestionStemLabel {
            label.text = stem.description
        }
    }
}