D11799 accidentally introduced a regression when replacing `return []` that was previously here. It was replaced with a call to `filterAndSetUserResults`, but the `return` was accidentally dropped, causing us to query the keyserver for the empty string from here. This happens in the background repeatedly as the keyserver connection status changes.
This addresses [ENG-8777](https://linear.app/comm/issue/ENG-8777/dont-crash-when-pressing-message-with-missing-author-username)
Depneds on D12680