Dashboard does not handle un-relate for profiles relation

[ca-scribner]

Reproduction steps:

• deploy and relate profile and dashboard operators
• after charms stabilise, remove Profile
• dashboards stays active in juju, but the dashboard itself does not work. If you log in, it says "unable to find kubeflow profile controller" or similar on the page

What was expected

I'd expect the Dashboard charmed operator to notice it is missing key dependencies and to set status/alert accordingly (eg: show Blocked or Error in juju status, maybe raise an alert rule, etc)