Help debugging exc_bad_acess

@IBOutlet weak var yourRankRetailLabel: UILabel!

@IBOutlet weak var barChartView2: BarChartView!


var employee: [String]!
var currentRank = ""


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.

        DataService.dataService.CURRENT_USER_REF.observeEventType(FEventType.Value, withBlock: { snapshot in //snap

        let rank = snapshot.value.objectForKey("rankretail") as! String

        self.yourRankRetailLabel.text = "You were ranked \(rank) in service sales last week!"
        self.currentRank = rank
        }, withCancelBlock: { error in
            print(error.description)
    })//snap


    employee = ["1491", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
    let unitsSold = [5.0, 4.0, 6.0, 3.0, 12.0, 16.0, 4.0, 18.0, 2.0, 4.0, 5.0, 4.0]

    setChart(employee, values: unitsSold)




}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.



    }

func setChart(dataPoints: [String], values: [Double]) {
    barChartView2.noDataText = "You need to provide data for the chart."

    var dataEntries: [BarChartDataEntry] = []
    for i in 0..<dataPoints.count {
        let dataEntry = BarChartDataEntry(value: values[i], xIndex: i)
        dataEntries.append(dataEntry)
    }

    let chartDataSet = BarChartDataSet(yVals: dataEntries, label: "Units Sold")
    let chartData = BarChartData(xVals: employee, dataSet: chartDataSet)
    barChartView2.data = chartData