Swift For循环线程错误

Question

func randomroll () {

    var time = arc4random_uniform(10)

   while(time < 5)
   {
    time = arc4random_uniform(10)
   }

   for(var time1 = time; time1>=0; time1--) { //This is where I get the thread error
    ...
   }
 }

我得到的错误是Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

我是一名初学者快速的程序员，我确信我错过了一些明显的东西，希望有一些见解。谢谢。