Change status when a Person is unassigned

I’ve set up an automation which updates a status column when someone is added to the people column for a given sub-item.

This status column is then mirrored to its parent column, which gives a visual summary in the parent item, allowing for a quick scan of any parent items that have sub-items without an assigned person. For example, if a person is assigned for 5 out of 10 sub-items, when collapsed into its parent item, the summary status column in the parent item will show a bar that’s 50% coloured.

This means i can quickly scan each parent item without having to go searching through the sub-items to see if the sub-items have people assigned to them.

However i can’t seem to find a way to have to status change if People column is unassigned. Some thing like this:
“When person is unassigned change status column to something”

We often have to assign/un-assign/re-assign people throughout a day based on new information from clients. So keeping track of what sub-items are assigned a person at a glance is useful.

Yes. I could just have a status column that says assigned Yes/No and manually updated it, but i’d prefer it to be automated to avoid human error.