Fix endless pipeline status loop when no pipeline was triggered

What does this MR do and why?

In the pipeline editor if you make a commit that does not trigger a new pipeline, a user is presented with a loading icon that never ends until they create a commit that triggers a pipeline.

This MR fixes that by showing a fetch error if there is no pipeline.

Screenshots or screen recordings

before	after

How to set up and validate locally

How to reproduce

1. Add the following snippet to your config in the pipeline editor

workflow:
  rules:
    - if: "$CI_COMMIT_BRANCH"
      changes:
        - ${TF_ROOT}/*.tf

1. Hit the commit button in the editor
2. Pipeline status will spin forever

This should be fixed now!

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #336664 (closed)