A group's members are automatically the meeting's participants, so the
Invite-participants, Invite-by-email and "Guests must be admitted by host"
sections are noise there. openScheduleModal now omits them when a group id is
present (inviteBlock is empty), and the email/participant/lobby handlers are
null-guarded so the save path still works without those fields.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>