CI_ENVIRONMENT_SLUG is null for any new branches

Summary

All new branches created set CI_ENVIRONMENT_SLUG to empty string (null). Existing branches work fine.

This issue only appeared after the most recent 10.5 release candidate deployment.

(Bring back the deployment announcement banners. Your deployments are not stable enough to remove those. Also please stop deploying release candidates to prod!!)

Steps to reproduce

Run CI on master. Runs perfectly. Create branch off master, run CI again. Watch CI crash and burn because CI_ENVIRONMENT_SLUG is null.

What is the current bug behavior?

CI_ENVIRONMENT_SLUG is null for all new branches.

What is the expected correct behavior?

It shouldn't be null...because we set it in gitlab-ci.yml

Relevant logs and/or screenshots

Job in question

Deploy ReviewApp:
    <<: *kube_deploy
    stage: Dev Deploy
    variables:
        CONTAINER_IMAGE: $CONTAINER_TEST_IMAGE
    environment:
        name: review/$CI_COMMIT_REF_SLUG            # CI_COMMIT_REF_SLUG is not null
        on_stop: Delete ReviewApp                   # CI_ENVIRONMENT_SLUG is null in the job
    only:
        - branches
    except:
        - master

Output of checks

This bug is on gitlab.com