System Settings - no categories for upload document - Introduce an error message 'At least one category must be set up'.

D1187
When I delete all the categories from either 'Upload Document' field and click 'Update', nothing happens (no confirmation no error prompt). I then check on Employee and it turns out the deletion did not take effect.

D1188
As an extension of D1187 - If I delete all the existing categories and add a new one, I was able to click on 'Update' and save. However, on refresh, I can see one of the categories that I deleted got restored. My guess is the delete cannot be processed because there are documents tied to that category

The validation should be done on deletion of the category instead of restoring after deletion. It can show a prompt of 'Category cannot be deleted as there are documents associated with it.'