Ref T13614. When an omnipotent user calls "synchronizeWorkingCopyBeforeWrite()", we record a WorkingCopyVersion record with a null "userPHID". The UI then renders this as "Unknown Object (????)".
Improve this behavior:
- When no PHID is available, just render nothing in the UI (this doesn't seem meaningfully different from no version existing at all).
- Allow callers to provide an acting user PHID, similar to Editor.
There's currently no way to perform this kind of write legitimately in the upstream, but T13614 is providing one.