[web] Fix channel deletion problem

Summary: Because of D8513, channel, subchannel, and thread deletion stopped working. This diff fixes this issue.

Test Plan: Run web app and check if channel, subchannel, and thread deletion are working.

Reviewers: ashoat, tomek

Reviewed By: ashoat

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8528