Swift 4认为数组不是空的

这是我的代码:

import UIKit


// Here we store our quotes
let quotesMain = ["You can do anything, but not everything.",
                  "The richest man is not he who has the most, but he who needs the least.",
                  "You miss 100 percent of the shots you never take."]

var quoteList = quotesMain
var amountQuotes = quoteList.count


class ViewController: UIViewController {

    //Here we can see the quotes appear
    @IBOutlet weak var quotesDisplay: UILabel!


    // When user clicks the button/screen
    @IBAction func newQuote(_ sender: Any) {

        let randomPick = Int(arc4random_uniform(UInt32(quoteList.count)))
        print(randomPick)
        quotesDisplay.text = (quoteList[randomPick])

        quoteList.remove(at: randomPick)

        // empty check
        if quoteList.isEmpty {
            quotesDisplay.text = "Ohnoes! We ran out of quotes, time to restore"

            // ask for restore
            quoteList += quotesMain
        }
    }


}