bug

Warning displayed in console about internal error of React performance measurement code.

``` js
import React from 'react';
import { render } from 'react-dom';
import Perf from 'react-addons-perf';
import { browserHistory, Router } from 'react-router';

import routes from './routes';
import persist from 'altFlux/persist';

persist('docs');

const target = document.getElementById('app');

Perf.start();

render(
  <Router
    routes={routes}
    history={browserHistory}
  />,
  target,
  () => {
    Perf.stop();
    Perf.printWasted();
  }
);
```

![screen shot 2016-05-23 at 9 21 08 am](https://cloud.githubusercontent.com/assets/91464/15472297/5e440d48-20c8-11e6-99d7-363f6d1bdcce.png)

15.1.0
Google Chrome

componentDidMount: emptyFunction,
      componentWillReceiveProps: emptyFunction,
      componentWillUpdate: emptyFunction,
      componentDidUpdate: emptyFunction,
      componentWillUnmount: emptyFunction,
      render: emptyFunction.thatReturnsNull,
    });
  });
  afterEach(function() {
    if (console.table.isFake) {
      delete console.table;
    }
  });
  function measure(fn) {
    ReactPerf.start();
    fn();
    ReactPerf.stop();
    
    ReactPerf.getWasted();
    ReactPerf.getInclusive();
    ReactPerf.getExclusive();
    ReactPerf.getOperations();
    return ReactPerf.getLastMeasurements();
  }
  it('should count no-op update as waste', function() {
    var container = document.createElement('div');
    ReactDOM.render(<App />, container);
    var measurements = measure(() => {
      ReactDOM.render(<App />, container);
    });