Filter items form confusion

[taylor-steve]

During testing it was noticed that the "Filter items" (Configuration > General > Filter items) form seems to have no way to remove an applied filter. After a user submits the form with both field and value, if they blank out both fields and resubmit there is a flash message stating
Field can't be blank<br/>Value can't be blank

It might be nice to be able to remove a filter. We had to create a new exhibit to continue testing.

If there's a reason removing a filter isn't technically possible, we may want to communicate that to the user.

[cbeer]

Is there a real-world use case for a single exhibit to show every indexed item? I know there's one the single-exhibit case (using the application-wideSpotlight::Engine.config.filter_resources_by_exhibit = false), but I'm not sure what not filtering at all would accomplish (and there's a reason this page is there just for superadmins 🤷‍♂️ )