_train_details: fix uninitialized value warning

        <a class="smallbutton" href="/carriage-formation?<%= $departure->{wr_link} %>&amp;e=<%= $departure->{wr_direction} // '' %>"><i class="material-icons" aria-hidden="true">train</i> <%= $departure->{wr_text} || 'Wagen' %>

        </a>

%     }

%     if ($departure->{trip_id} and param('dbris') eq 'bahn.de') {

%     if ($departure->{trip_id} and param('dbris') and param('dbris') eq 'bahn.de') {

        <a class="smallbutton" href="https://bahn.expert/details/x/h/<%= Mojo::Util::url_escape( $departure->{trip_id} ) %>"><img src="/static/icons/bahn-expert.svg">Details</a>

%     } elsif ($departure->{train_type} and $departure->{train_no} and (not param('hafas') or param('hafas') eq 'DB')) {

        <a class="smallbutton" href="https://bahn.expert/details/<%= $departure->{train_type} %>%20<%= $departure->{train_no} %>/<%= ($departure->{date} // DateTime->now(time_zone => 'Europe/Berlin'))->iso8601 %>?evaNumberAlongRoute=<%= $departure->{eva} %>"><img src="/static/icons/bahn-expert.svg">Details</a>