Do not throw error on nil repository in resolver.
Created by: efritz
The change added https://github.com/sourcegraph/sourcegraph/commit/5861ade4b66ab6a8e1670c3e89cc1e097a9e1763 will return an unexpected error from the Repository resolver, when nil is an acceptable result (the schema is not a required repository). This was breaking most of the regression tests (context) as the retry loop wasn't expecting a non-formatted error.
@sourcegraph/core-services : is this now the correct respond type (nil repository, no error) or should it be different (nil repository, formatted error with correct code)?
Update: it appears it should be nil, nil: https://github.com/sourcegraph/sourcegraph/blame/9bde612d46032964ecee8e586194a48b3279676d/cmd/frontend/graphqlbackend/graphqlbackend.go#L412