Author searches report 'no results', should hint to use type:commit or type:diff

Created by: rrhyne

Some filters result in 'No result' and do not help the user understand why. Example:

1. Search repo:sourcgraph/sourcegraph author:[email protected]
2. Note the user has not included type commit or diff
3. Run search

Expected behavior:

A tip is provided that author searches require type:commit or type:diff.

Actual behavior:

3. Receive the "No Results" banner

Identify combinations of languages and types which are not compatible and add hints for the user as to how to produce a valid result.