The "None" and "Custom icon" cases where using the same value for icon
type, which resulted in both options showing the application icon.
Use -1 to indicate the custom option, and treat all other options
the same.
Task-number: QTBUG-76916
Change-Id: Ib715f5d328175bd6e221b3f507087954fa542838
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>