further fixes

this makes a broken component at least show "broken", although there are still issues:

- initial designer load, adding component `secretrobotron/component-email` works. HTMLImports does not throw errors, CustomeElement does not throw errors.
- reloading the page, 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. Initial adding is correct, reload parsing breaks for some reason
2. this component shouldn't work. Initial adding should have failed, rather than only subsequent loading.