It's correct, though. The URI scheme for HTTPS may always include a domain name, but my-app: is just as valid a URL as anything else. A protocol where everything is optional and the default opens a screen with all fields empty is valid, though unlikely.

For instance, an empty mailto: will reliably launch an email client, even if no address is specified. I think it's the second most used protocol in web links, after HTTP(S).

If you want to to URL parsing by brute forcing URL constructors, you probably don't want application URLs in the first place. You should probably start with https:// and http://, or make use of the weird double slash HTTP introduced into the URL by matching on :// instead.