[dom] Should null be treated as an empty string, "null", or an error? (#97)

https://dom.spec.whatwg.org/#interface-characterdata

`appendData`, `insertData`, `deleteData`, and `replaceData` do not specify what to do when passed `null`. I did notice that the `data` parameter is specified as `DOMString`, not `DOMString?`.

Currently, Mozilla Firefox and Google Chrome treat `null` as if it were `"null"` (I guess by converting `null` to `String` internally when called);  and I am not sure whether to follow that behaviour in a DOM library I am writing (i.e. converting `data` to `String` where possible, and throwing otherwise).

Example
-------

```js
let text = new Text();
text.appendData(null);
console.log(text.data);  // => "null"
```


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Reply to this email directly or view it on GitHub:
https://github.com/whatwg/dom/issues/97