I'm also experiencing this issue, after adding the ionic-web-platform plugin (as part of the tutorial) my app would no longer load in emualtors and on devices, I've verified this by copying over my code to a new project which works completely perfectly until I run 'ionic add ionic-web-platform' etc etc, and to make matters worse, the plugin isn't properly removed from ionic.bundle.min.js after running 'ionic remove ionic-web-platform' command.
Would really like an updated tutorial/fix for this so I can use push notifications in my project!