https://bugs.winehq.org/show_bug.cgi?id=45023
--- Comment #4 from François Gouget fgouget@codeweavers.com ---
17. Optional enum properties are not really supported
CreateEnumPropertyDescriptor() takes an $IsRequired parameter. But although it is possible to set it to False, various DBI/Collection/Item places generate errors when such an enum field is set to undef.