react-error-overlay: uncaught typeerror on using right/left arrow

Created by: Gandem

Hello !

First of all thanks a lot for the upgrade and the hard work, create-react-app is completely awesome 😄 !

This issue was discovered when updating to react-scripts@1.0.0

Description

On launching an empty app created with create-react-app, and using right/left arrow on the keyboard (when no overlay error is present) it logs an error in the console:

Uncaught TypeError: Cannot read property 'error' of undefined
    at renderErrorByIndex (overlay.js:66)
    at switchError (overlay.js:86)
    at shortcutHandler (overlay.js:145)
    at keyHandler (shortcuts.js:17)

Reproducible Demo

I could reproduce this error on a new react project created with create-react-app, as well as old projects I upgraded.

For info, I'm on Mac OSX Sierra on Chrome 57.

I would be glad to send a Pull Request and work on this issue, if someone could give me some hints to what's actually happening on here !