further fixes

this makes a broken component at least show "broken", although there are still issues, currently revealed by adding the component `secretrobotron/component-email`.

- initial adding: HTMLImports does not throw errors, CustomeElement does not throw errors.
- reloading the designer: with this component saved for my login now causes either the HTMLImports code path to throw an error somewhere when resolving an async XHR (without any network errors according to debugger, so: mystery), or it fails parsing the component. In both cases the component is correctly left as flagged "broken" but this means we are in either of 2 situations:

1. this component works, and is not supposed to show up as broken, ever; Initial adding is correct, parsing during a designer-page-load after adding the component, when it's retrieved as part of the user logging in, breaks for some reason.
2. this component shouldn't work, and should not be added as usable component. Initial adding should throw errors *somewhere*, rather than only breaking on subsequent designer loading.