Calling concat() on freezed array without parameter will add undefined item to the end of array

[psulek]

Lets have this code:

const { freeze } = require("freeze-mutate");
const obj = freeze({a: [1,2]};
const newArr = obj.a.concat();

Now newArr will have 3 items: 1, 2 and undefined which is wrong and undefined should not be added.
Also calling contact on array without any parameter is valid in JS and does not add undefined.

I can make PR if u want? @eram

[eram]

@psulek sure. go ahead