Infinite GI spinner on loading when service worker missing

[taoeffect]

Problem

There are some situations in which this is thrown from service-worker.js:

const swRpc = (() => {
  if (!navigator.serviceWorker) {
    throw new Error('Missing service worker object')
  }

If that happens the GI logo just spins:

This is bad UX.

This can happen for example when GI is being run from within a VM, and then the host accesses it via http://<vm-ip>:3000

Solution

At the very least we should display some kind of error message to the user that tells us what the problem is.