[web] Allow nullable threadID in useOnClickThread

Summary: I need this for next diff, context here

Test Plan: Flow, tested with next diffs

Reviewers: palys-swm, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, palys-swm, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D996