Add safe guard for pipeline without stage name

What does this MR do and why?

Adds safeguard for an issue where a pipeline was returned without a stage name. This caused the tab vue app to blow up since the name property was non-existent. We believe root cause is on the BE but we can add a safeguard for now if users end up in this situation.

Example pipeline reported: https://gitlab.com/gitlab-org/gitlab/-/pipelines/644740078/builds

Screenshots or screen recordings

How to set up and validate locally

1. Visit example pipeline in MR.
2. Change job locally to job = { stage: { id: '' } } in stageName method. Test with optional chaining and without new changes.

MR acceptance checklist

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