Updating packages in the Preact Tutorial breaks it

I’m following this tutorial which is a little dated now:

https://developer.okta.com/blog/2017/10/19/build-a-preact-app-with-authentication

The code for which is here:

https://github.com/oktadeveloper/okta-preact-widget-example

If I check out the code with the same versions from the github repo and substitute in my client ID and redirect URI it works fine under node 10 in docker.

If I update all packages to their current versions, remove import "@okta/okta-signin-widget/dist/css/okta-theme.css"; from src/lib/auth.js (as it’s apparently been removed since then) and run it, it will then build OK. But I get the following error in all the Auth class methods calling tokenManager in https://github.com/oktadeveloper/okta-preact-widget-example/blob/master/src/lib/auth.js:

this.widget.tokenManager is undefined

Has the sign in widget API changed since this tutorial was written and if so how do I address that bug? - I’d like to fix it and PR the fix to the git repo so the tutorial works with current versions but I’m a bit of a node newbie so looking for some help.

Thanks in advance, Matt.