API: Inconsistency between `GET /settings/profile` and `PUT /settings/profile`

[marhei]

If the user has disabled automatic status hiding, the privacyHideDays key will return 0, but you need to set the same key to null on the PUT /settings/profile endpoint to avoid getting an error that it should be at least 1. For consistency, the GET /settings/profile endpoint should also return null if this option is disabled.