like the user has made a selection, but they've only selected one
of the projection category headings and so when they click OK they
see no change.
Now instead we disable the OK button in this dialog whenever the
user has a non-crs list item selected.
of a layer or project is unknown
Because:
1. It clearly indicates that the current CRS for the object is unknown
2. It lets users see the full WKT/proj definition of the CRS, and allows
them to copy this definition
3. Avoids loss of CRS information when just opening and accepting the dialog
Refs #33458
