Due to the way we store revision metadata for package loader. A snapshot can
reference a previous revision with metadata that are not nixguix related. Thus,
the expected "integrity" (from the nixguix loader point of view) field is not
found. Which makes the loader crash.
This diff allows the loader to continue its work without crashing by
considering such revision to be fetched again.
pros:
- the loader works
cons:
- redo all the ingestion for noop in the storage side
Related to T2371
Related to T2411