The value of NColorRoles got changed since 5.11. It introduced one more
role called "PlaceholderText" in the ColorRole enumeration.
When using QDataStream (5.12) to read QPalette objects from a file
written by 5.9 (<5.11), the processing results are inconsistent.
Fixes: QTBUG-74885
Change-Id: I14d57f9603a26e5890b4fd57c7e464c5b38eb3f2
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>