Knob set still active and navigable after removing all mappings

[danngreen]

See:
https://forum.4ms.info/t/removing-a-knob-set-and-patch-view/347

[danngreen]

The part to implement for the Issue is removing a knobset after all knob mappings are removed. There might be a slight annoyance if a custom name was set and the user removed all mappings, intending to add different ones, but I think this is an edge case and an easy workaround is to not delete all mappings at once (or add the custom name)

The other issues mentioned: Knob set organizational tools (re-ordering, clear-all, delete) would be a separate issue