ports-mgmt/pkg: Backport bug fix needed for 15.0

This adds a patch (7ea9566835a82f111d7771f58168babc5e0dde6a) which
fixes a release-build-breaking bug in pkg(8). It is now in the pkg
repository but the 15.0 release process can't wait for a new pkg
release to happen so I'm pulling the bug fix in here instead.

With hat: re@
Reviewed by: kevans
Differential Revision: https://reviews.freebsd.org/D53310

(cherry picked from commit 12d2f0b8d4607de67604922c58292cde6f4a1cbd)