tdf#112153: Set button theme properly

Change-Id: I0665880c0d0348fcbb3bcf04d9172405c8e31eb7
Reviewed-on: https://gerrit.libreoffice.org/48334Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tor Lillqvist <tml@collabora.com>

vcl/osx/salnativewidgets.cxx

@@ -106,11 +106,11 @@ static ThemeButtonValue ImplGetButtonValue( ButtonValue aButtonValue )
             break;
 
         case ButtonValue::Off:
+        case ButtonValue::DontKnow:
             return kThemeButtonOff;
             break;
 
         case ButtonValue::Mixed:
-        case ButtonValue::DontKnow:
         default:
             return kThemeButtonMixed;
             break;