If you're talking about either the bad (pyramid of doom) code in Myth #1 - or the good code there, then it is indeed protecting against null values in the JSON. When you try to cast with `as? String`, it returns nil when there's a null value in the JSON and the code in the `if` block is skipped (and the `else` block is executed if one exists).
The point is that neither of them are good. Nulls should be expected in json objects, so why write the parsing inside a conditional that will fail when one is encountered?