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

**What is the current behavior?**
The shallow renderer defaults a class component's state to empty object if it's not set. "Real" renderers don't seem to do this, so a component can render successfully in the shallow renderer, but fail at runtime in the browser with a null reference error.

**If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem.**
Here is ReactDOM's behavior (crashes reading an uninitialized state value): https://codesandbox.io/s/4jv82zmp0
Here is the shallow renderer behavior (component able to render): https://codesandbox.io/s/pp733nrxzq

**What is the expected behavior?**
They initialize state in the same way.

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
React 16. This wasn't an issue in React 15.
static contextTypes = {
        name: PropTypes.string,
      };
      render() {
        return <div />;
      }
    }
    const shallowRenderer = createRenderer();
    const result = shallowRenderer.render(<SimpleComponent />);
    expect(result).toEqual(<div />);
  });
  it('passes expected params to component lifecycle methods', () => {
    const componentDidUpdateParams = [];
    const componentWillReceivePropsParams = [];
    const componentWillUpdateParams = [];
    const setStateParams = [];
    const shouldComponentUpdateParams = [];
    const initialProp = {prop: 'init prop'};
    const initialState = {state: 'init state'};
    const initialContext = {context: 'init context'};
    const updatedState = {state: 'updated state'};
    const updatedProp = {prop: 'updated prop'};
    const updatedContext = {context: 'updated context'};
    class SimpleComponent extends React.Component {