Permutation not work if size is higher than the number of elements in the set

Hello,

The permutation function doesn't work if the parameter **size** is higher than the length of the parameter **arr**. 
Example

**Works**
```js
G.permutation(['0', '1', '2', '3'], 4);
````

**Doesn't work**
```js
G.permutation(['0', '1', '2', '3'], 5);
````