这是Apple Watch beta开发版中的错误吗？

Question

看看这些短代码产生的差异

var animals: [Character] = ["","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""]

func setBoard() {
    var charToChoose = maxButtons / 2
    var charChosen:Character = ""
    var j = 0
    for var i = 0; i < charToChoose; i++ {
        let randomIndex = Int(arc4random_uniform(UInt32(animals.count)))
        println("randomIndex = \(randomIndex)")
        charChosen = animals[randomIndex]
        println("charChosen = \(charChosen)")
        boardArray[j] = charChosen
        //j++
    }
    println("printing of board array = \(boardArray)")

    }

使用Xcode 6.1.1（6A2008a）的输出

randomIndex = 39 charChosen =  
randomIndex = 36 charChosen =  
randomIndex = 50 charChosen = 
randomIndex = 4 charChosen =  
randomIndex = 2 charChosen = 
randomIndex = 1 charChosen =  
randomIndex = 38 charChosen = 
randomIndex = 3 charChosen =  
printing of board array = [, , , , , , , ]

仅在watchkit extenxion中使用Xcode 6.2（6C121）的输出

randomIndex = 18 charChosen =  
randomIndex = 7 charCsen =  
randomIndex = 50 charChon = \360\237\220
randomIndex = 40 charChosen = \360\237\220
randomIndex = 12 charChosen =  
randomIndex 3 charChosen =  
randomIndex = 5 charChosen = \360
randomIndex = 50
charChosen = \360\237\220

printing of board array = [, , , , , \360\237