CI: Fix CI_HELPER

CI: Fix CI_HELPER

Commit 18d3c529fa4ab8dafcf6c147cf3cb55792d8ca10 caused CI_HELPER to be
set to "''" (two single quotes), leading to an error when test.sh tries
to source $CI_HELPER.

CI_HELPER is not set anywhere else and not passed into the container
environment, so there is no need to test if it has a value.

This fixes the value of CI_HELPER.

Fixes: 18d3c529fa4a ("github-ci: error on any shell errors")
Signed-off-by: Jeffery To <jeffery.to@gmail.com>
(cherry picked from commit 562f5df67fd9436dface35a410e9ce591d9a2894)