Machine view is stuck on loading indicator when ELK throws

[farskid]

Description

In case of any runtime errors in ELK and how it renders the machine configuration, the viz is stuck on the loading screen.

Expected Result

An error screen is rendered showing the error message or even the error stack. Potentially, a way to report the bug to the Stately team is a bonus.

Actual Result

Loading screen is shown forever.

Reproduction

Try this machine: https://stately.ai/viz/161452bd-efb9-4ee5-bd93-879401dedfd5

[zgotsch]

@davidkpiano This example is fixed by #387.