Behavior of .replace() method

[johny65]

Check this:

let $val = null;
select $val.replace('some', 'thing');
/* returns 'some' */

The result is 'some', i.e. the string I want to be replaced. This happens when the input string is null, is this behavior correct or is it a bug? If the input string is empty, then it works as expected:

let $val = '';
select $val.replace('some', 'thing');
/* return '' */