Fix crash in ProfileSettings; clone selected profile settings to new profile

- If there is no selection only enable the "New" button, this fixes a
  crash if you select a profile, then Ctrl+Click to unselect it, the set
  as default button would still be enabled and clicking it caused a crash

- If a profile is selected, clone its properties, otherwise the fallback
  profile properties will be used, this more expected

(cherry picked from commit bc41efd8)