[PATCH v2] msxml3: Null check new child in insertBefore.

[Nikolay Sivov]

Please split this in two patches, one for document and one for element node.
> +    /* NULL to document */
> +    V_VT(&v) = VT_NULL;
> +    node = (void*)0xdeadbeef;
> +    hr = IXMLDOMDocument_insertBefore(doc, (IXMLDOMNode*)NULL, v, &node);
> +    ok(hr == E_INVALIDARG, "got 0x%08x\n", hr);
> +    ok(node == (void*)0xdeadbeef, "got %p\n", node);
> +
> You don't need to cast NULL.