builder: Inherit parent version for inherited extension
builder: Inherit parent version for inherited extension

If you inherit an extension, and it has no explicit version, then
use the version of the parent, as that is what would automatically
be used for the parent.

handsome-feng/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak