Nativization is not perfect, not all things are supported not all practice cases may work and when this happens it usually gives compilation errors.
EditorWidgets sounds like it tries to natiovize new UMG editor Widgets, editor APIs are not accessible in packaging (since module obviously is compiled to non-editor build of engine), so i would raport a bug as this should not happen
and put editor widgets to nativization exclusion, you can read about it here: