search: handle zoekt repo name being out of sync

Created by: keegancsmith

We have observed (one) panic in production due to repoRev being nil. This can only happen if zoekt returns results with a repository name different to what Sourcegraph thinks it is. This was always a possibility (until zoekt updates indexes), but it only affected us since we have started searching repos by ID since last week. Previously it was by name, so the repo would be skipped and not returned.