Inconsistent "no reference" state shown for workspaced elements
A workspaced element uses a local workspace, which might not have been created using a cached source with a known ref.
When a workspaced element has no ref (refs are not stored with the project and it has never been tracked), then it cannot be built because BuildStream complains that it's ref is unknown.
This is wrong because BuildStream does not use the upstream, project decided source for a workspaced element.