**Do you want to request a *feature* or report a *bug*?**
Bug

**What is the current behavior?**
I've started recieving this warning about my SVGs which is using [feGaussianBlur](https://developer.mozilla.org/en-US/docs/Web/SVG/Element/feGaussianBlur): 
`Warning: Expected server HTML to contain a matching <feGaussianBlur> in <filter>.`

**What is the expected behavior?**
Should be no warnings because there are no difference.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
Such behavior started right after updating to `React 16.0.0-rc.3` and never happened with `React 15.6.1`
} else {
          expect(e.childNodes.length).toBe(2);
          expectTextNode(e.childNodes[0], 'foo');
          expectTextNode(e.childNodes[1], '40');
        }
      });
    });
    describe('null, false, and undefined children', function() {
      itRenders('null single child as blank', async render => {
        const e = await render(<div>{null}</div>);
        expect(e.childNodes.length).toBe(0);
      });
      itRenders('false single child as blank', async render => {
        const e = await render(<div>{false}</div>);
        expect(e.childNodes.length).toBe(0);
      });
      itRenders('undefined single child as blank', async render => {
        const e = await render(<div>{undefined}</div>);
        expect(e.childNodes.length).toBe(0);
      });
      itRenders('a null component children as empty', async render => {
        const NullComponent = () => null;
        const e = await render(<div><NullComponent /></div>);
        expect(e.childNodes.length).toBe(0);
      });
      itRenders('null children as blank', async render => {
        const e = await render(<div>{null}foo</div>);
        expect(e.childNodes.length).toBe(1);
        expectTextNode(e.childNodes[0], 'foo');
      });