Function works but a 53rd undefined element gets added to the array when the number of shuffles gets too high.

```
function shuffle(deck , shuffles) {
    for(let i = 0; i < shuffles; i++) {
     let first = Math.floor(Math.random() * 53);
     let secound = Math.floor(Math.random() * 53);
     let fShuffle = deck[first];
     let sShuffle = deck[secound];
     deck[first] = sShuffle;
     deck[secound] = fShuffle;
    }
    return deck;
  }

```

It shuffles everything but an undefined element sneaks in and I'm not sure how to get rid of it.