Uncaught TypeError: Cannot read property 'push' of undefined (React-Router-Dom)

I have a Dashboard with rotating slides, each of which has a corresponding tab in Bldgs. Both Dashboard.js and Bldgs.js are children to my App.js.

When a user clicks on a specific slide A in Dashboard.js, Dashboard needs to tell App.js so that App can tell Bldgs.js to have tab A displayed when it routes to Bldgs.

I believe that I am passing the correct index value from Dashboard up to App and down to Bldgs. However, an error is being thrown in my App.js file stating:

Uncaught TypeError: Cannot read property 'push' of undefined

My code was working fine before I started passing my handleClick() function to my Dashboard component.

Index.js

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import './index.css';
import injectTapEventPlugin from 'react-tap-event-plugin';
import MuiThemeProvider from 'material-ui/styles/MuiThemeProvider';
import { BrowserRouter as Router } from 'react-router-dom';
import { hashHistory } from 'react-router';

// Needed for onTouchTap
// http://stackoverflow.com/a/34015469/988941
injectTapEventPlugin();

ReactDOM.render(
  <MuiThemeProvider>
    <Router history={hashHistory}>
      <App />
    </Router>
  </MuiThemeProvider>,
  document.getElementById('root')
);

App.js

import React from 'react';
import { Route } from 'react-router-dom';
import Dashboard from './Dashboard';
import Bldgs from './Bldgs';

var selectedTab;

class App extends React.Component {
  constructor(props) {
    super(props);
    this.handleClick = this.handleClick.bind(this);
    selectedTab = 0;
  }

  handleClick(value) {
    selectedTab = value;
    // console.log(selectedTab);
    this.props.history.push('/Bldgs');
    // console.log(this.props);
  }

  render() {
    var _this = this;

    return (
      <div>
        <Route exact path="/" render={(props) => <Dashboard {...props} handleClick={_this.handleClick} />} />
        <Route path="/Bldgs" component={Bldgs} curTab={selectedTab} />
      </div>
    );
  }
}

export default App;

Dashboard.js

import React, { Component } from 'react';
import './Dashboard.css';
import { AutoRotatingCarousel, Slide } from 'material-auto-rotating-carousel';
...

var curIndex;

class Dashboard extends Component {
  constructor(props) {
    super(props);
    this.handleEnter = this.handleEnter.bind(this);
    this.handleChange = this.handleChange.bind(this);
    curIndex = 0;
  }

  handleEnter(e) {
    // console.log(curIndex);
    this.props.handleClick(curIndex);
  }

  handleChange(value) {
    // console.log(value);
    curIndex = value;
  }

...
}

export default Dashboard;

Bldgs.js

...
var curTab;

class Bldgs extends Component {
  constructor(props) {
    super(props);
    this.handleChange = this.handleChange.bind(this);
    this.goHome = this.goHome.bind(this);
    curTab = 0;
  }

  handleChange(value) {
    this.setState({'selectedTab': value});
    console.log(this.state);
  }

  goHome(e) {
    this.props.history.push('/');
  }

...
}

export default Bldgs;

via Mike