This fixes another regression introduced with
1f466ed6be932526fc69e72ffd50390691d0d382, which affected the packages bitmask,
hime, hime, nimf and vorta.
The fix is to provide a default qt-major-version when #:qtbase is missing,
such as when borrowing the qt-wrap phase in a package not using the Qt build
system.
* guix/build/qt-utils.scm (wrap-all-qt-programs)[qt-major-version]: Fall-back
to %default-qt-major-version when #:qtbase is #f.
Reported-by: John Kehayias <john.kehayias@protonmail.com> and others.
