fix: broken suggestions due to empty language suggestions
Created by: attfarhan
Fixes https://github.com/sourcegraph/sourcegraph/issues/6126.
I was/still am not able to get a completely reliable repro on the issue, but when it did occur, I found that we were returning empty lang
suggestions, added in https://github.com/sourcegraph/sourcegraph/pull/5859. When we got these lang suggestions on the frontend, we handled them by returning null
instead of a search row, causing there to be a bunch of empty, but selectable, entries in the DOM.