carriage formation preview: fix direction == 0

%   if (my $wr = $departure->{wr}) {

      <div class="wagonorder-preview">

%     my @wagons = $wr->wagons;

%     my $direction = $wr->direction ? $wr->direction == 100 ? '→' : '←' : q{};

%     my $direction = defined $wr->direction ? $wr->direction == 100 ? '→' : '←' : q{};

%     if ($departure->{direction}) {

%       $direction = $departure->{direction} eq 'l' ? '◀' : '▶';

%       if (($departure->{direction} eq 'l' ? 0 : 100) != $wr->direction) {