Surface NoGroundingFound error to end user

[kkaris]

If you run a query using namespace: auto for an entity that doesn't have a grounding, e.g. VE-821 the search responds with a Failed to load search results: (500) .. Using Ground with GILDA first makes it clear that there is no grounding for the entity. It would be useful to surface this information for the namespace: auto search as well to the end user so that it differs from a 'true' internal server error.