Null or undefined values

[theblomskog]

If target values are null or undefined, sorting becomes corrupt.
I have cloned your project and fixed it so it fits my use-case, where some values in rows might be null or undefined.
I just implemented a compare function as follows:
static compare(a: any, b: any ) {
if(a == null && b == null) return 0;
if(a != null && b == null) return -1;
if(a == null && b != null) return 1
return a > b ? 1 : -1;
}
And replaced some of the logic.
I also created som more tests to verify it.
Would you be intressted in me making a pull request?

[VadimDez]

If it makes the project better - sure!

[VadimDez]

Fixed by #44, released in 1.1.3