fix: define `repos_from_e` to fix builds with a custom `roomservice.xml`

Description

Passing in a custom local_manifests/roomservice.xml triggers roomservice.py to run in depsonly mode, in which repos_from_e doesn't get defined. An exception is thrown once add_to_manifest tries to access it, so this small change makes sure it is always defined. The second commit contains just two minor whitespace fixes.

Issue(s)

e/backlog#5881

Test environment

registry.gitlab.e.foundation:5000/e/os/docker-lineage-cicd:community

Test procedures

Build a ROM with a custom local_manifests/roomservice.xml.

Technical details

Screenshots

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation