Instead of taking an `ActUser` as a property of the
`MctRestrictApplicationsDialog`, take the display name which we would
have queried from it.
This will allow the restrict applications dialog to be used in
situations where an `ActUser` isn’t available, such as when setting the
parental controls for a yet-to-be-created user.
This breaks the `MctRestrictApplicationsDialog` API, but the previous
API hadn’t yet been released.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
6b45ad9f76