code: public ScreenParent makeScreen(ScreenLoc itsLocation, ComponentParent parentScreen, int iDocMode, Map<String, Object> properties)
      {
          return null;    // Not implemented in thin.
      }
docs: Create a default document for file maintenance or file display.
  Usually overidden in the file's record class.
  @param itsLocation The location of the screen in the parentScreen (usually null here).
  @param parentScreen The parent screen.
  @param iDocMode The type of screen to create (MAINT/DISPLAY/SELECT/MENU/etc).
  @return The new screen.