My app does not start, "cannot set _config of undefined in components/app.js"

I recently updated to ionic-angular 2.0.0-beta.10 and manually included the zone.js and reflect-metadata polyfills in the index.html of my app.
After that, when I start the app, I get an error saying _config cannot be set to this, since this is undefined in ionic-angular/components/app/app.js.
Can anyone shed some light on what might be going wrong here? Can this be undefined due to an error in my code? But, the app was working fine until I updated it to beta 10. And btw, my app is written in JS and not TS.