Translucent white covering my button in UITableView

Question

I've set constraints and everything but there's a translucent white "screen" covering the lower part of my screen. It's not fixed to my tableview because when I scroll down the button gets pulled up and is visible but the screen stays there. At first I thought it was a rogue view but it's not so I'm not sure what's going on. Any pointers on what I should be looking at to solve this problem? Here's a picture:

Here is my code (a little untidy because this is my first project in swift): import UIKit

class MainViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    @IBOutlet weak var buttonView: UIView!
    @IBOutlet weak var button: UIButton!
    @IBOutlet weak var tableView: UITableView!

    let manager = WorkoutDataSource()
    let gradientLayer = CAGradientLayer()
    var workouts = []
    override func viewDidLoad() {
        super.viewDidLoad()
        self.tableView.delegate = self
        self.tableView.dataSource = self
        self.workouts = manager.getWorkOuts()
        let borderAlpha : CGFloat = 0.7
        let cornerRadius : CGFloat = 5.0


        button.backgroundColor = UIColor.clearColor()
        button.layer.borderWidth = 1.0
       button.layer.borderColor = UIColor(white: 1.0, alpha: borderAlpha).CGColor
        button.layer.cornerRadius = cornerRadius

        let heightOfVisibleTableViewArea = tableView.bounds.height - topLayoutGuide.length - bottomLayoutGuide.length
        let numberOfRows = tableView.numberOfRowsInSection(0)

        tableView.rowHeight = heightOfVisibleTableViewArea / CGFloat(numberOfRows)


        let color1 = UIColor(hue: 0.9528, saturation: 0.4, brightness: 1, alpha: 1.0) /* #ff759d */
        let color2 = UIColor(hue: 0.0167, saturation: 0.25, brightness: 0.95, alpha: 1.0) /* #ffb1b1 */
        let color3 = UIColor(hue: 0.2528, saturation: 0.11, brightness: 0.85, alpha: 1.0) /* #f3bbb4 */
        let color4 =  UIColor(hue: 0.3833, saturation: 0.21, brightness: 0.91, alpha: 1.0) /* #cedbc2 */
        let color5 = UIColor(hue: 0.4417, saturation: 0.62, brightness: 0.97, alpha: 1.0) /* #b7eac7 */
        let color6 = UIColor(hue: 0.4528, saturation: 0.91, brightness: 0.81, alpha: 1.0) /* #12d19e */ /* #5ef9c3 */
        //let color7 = UIColor(hue: 0.5833, saturation: 0.7, brightness: 0.68, alpha: 1.0) /* #346fae */
        let color7 = UIColor.flatNavyBlueColorDark()
        gradientLayer.colors = [color1, color2, color3, color4, color5, color6, color7]


         view.backgroundColor = UIColor.flatNavyBlueColorDark()

        setTableViewBackgroundGradient(color7, bottomColor: color1)
        self.navigationController?.navigationBar.backgroundColor = UIColor.flatNavyBlueColorDark()!


        // Do any additional setup after loading the view, typically from a nib.

        // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int{
        return self.workouts.count
    }

    func setTableViewBackgroundGradient(topColor: UIColor, bottomColor: UIColor){

        let gradientBackgroundColors = [topColor.CGColor, bottomColor.CGColor]
        let gradientLocations = [0.0,1.0]

        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = gradientBackgroundColors
        gradientLayer.locations = gradientLocations

        gradientLayer.frame = tableView.bounds
        let backgroundView = UIView(frame: tableView.bounds)
        backgroundView.layer.insertSublayer(gradientLayer, atIndex: 0)
        tableView.backgroundView = backgroundView
    }

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

        let workout = self.workouts[indexPath.row] as? Workout
        let cell = tableView.dequeueReusableCellWithIdentifier("Cell") as? WorkoutCell
        cell!.textCellLabel?.text = workout?.title
        cell!.backgroundColor = workout?.color
        cell!.countLabel.text = "\(indexPath.row+1)"
        cell!.selectionStyle = UITableViewCellSelectionStyle.None
        cell!.backgroundColor = UIColor.clearColor()
        return cell!
    }
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        if(segue.identifier == "detailview"){
            let cell = sender as? WorkoutCell
            let indexPath = tableView.indexPathForCell(cell!)
            let nvc = segue.destinationViewController as? UINavigationController
            if let tmp = workouts[indexPath!.row] as? Workout{
                let dvc = nvc?.topViewController as! DetailViewController
                dvc.workout = tmp
            }

        }
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        self.tableView.contentInset = UIEdgeInsetsMake(0,0,55,0)
    }



}