* fix(invite): do not send empty queries for people search

The endpoint might return an error if an empty query is sent.

* fix(invite): add error logging for failed people directory requests

The error currently being passed through from $.getJSON ended up
being an empty string plus was not getting logged. So switch to
fetch to move along with jquery killing and log the error.

* fix(dial-in): add error logging for failed requests

* ref(invite): create a fetch helper to remove duplicate logic