[web] Swap order of conditions in ChatThreadComposer onSelectUserFromSearch

Summary:
This is safe because when sortedMembers in usePotentialMemberItems sets notFriendNotice, it also sets an alert.

Depends on D13543

Test Plan: Careful reading of the code indicates that this is a no-op

Reviewers: tomek, kamil, inka

Reviewed By: tomek

Differential Revision: https://phab.comm.dev/D13544