This fixes a regression introduced in commit 536c3ee.
* guix/profiles.scm (ca-certificate-bundle): When MANIFEST is empty,
make a trivial derivation.
* guix/scripts/package.scm (guix-package)[process-actions]: Pass
#:ca-certificate-bundle? to 'profile-generation'.
* tests/packages.scm ("--search-paths with pattern"): Likewise.
* tests/profiles.scm ("profile-derivation"): Likewise.