case: filter breaks searches with repo: filter if no other term is provided

Created by: attfarhan

• Sourcegraph version: Sourcegraph.com"

Steps to reproduce:

1. search for repo:sourcegraph case:no or any query with a repo: filter and case: filter and nothing else. notice that no results appear

Expected behavior:

I would expect the search to display the repository results. case:no is the default behavior, so it should show repos as if no case: was provided, and case:yes should show only repos that match the case provided to the filter.

Actual behavior:

No results