fix: possible error when GROVE_MFE_CDN_ORIGIN is undefined

Description

Fixes an error introduced in !36 (merged)

Supporting information

• Broken pipeline: https://gitlab.com/opencraft/devstacks/keith/grove-do/-/jobs/4366914527
• Fixed pipeline: https://gitlab.com/opencraft/devstacks/keith/grove-do/-/jobs/4367108863

Testing instructions

Check the linked pipelines

Checklist

If any of the items below is not applicable, do not remove them, but put a check in it.

• Git commit history is clean
• Git commits are following conventional-commit practices
• Unit tests are added/updated
• Documentation is added/updated