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

if (__DEV__) {
    var previousStartTime = currentFlushStartTime;
    var previousMeasurements = currentFlushMeasurements || [];
    var previousOperations = ReactHostOperationHistoryDevtool.getHistory();
    if (!isProfiling || currentFlushNesting === 0) {
      currentFlushStartTime = null;
      currentFlushMeasurements = null;
      clearHistory();
      return;
    }
    if (previousMeasurements.length || previousOperations.length) {
      var registeredIDs = ReactComponentTreeDevtool.getRegisteredIDs();
      flushHistory.push({
        duration: performanceNow() - previousStartTime,
        measurements: previousMeasurements || [],
        operations: previousOperations || [],
        treeSnapshot: getTreeSnapshot(registeredIDs),
      });
    }
    clearHistory();
    currentFlushStartTime = performanceNow();
    currentFlushMeasurements = [];
  }
}
function checkDebugID(debugID) {