my $mids = mids_for_index($mime);
$smsg //= bless { blob => '' }, 'PublicInbox::Smsg'; # test-only compat
$smsg->{mid} //= $mids->[0]; # v1 compatibility
my $mids = mids_for_index($mime);
$smsg //= bless { blob => '' }, 'PublicInbox::Smsg'; # test-only compat
$smsg->{mid} //= $mids->[0]; # v1 compatibility