if (i->main_subtitle()) {
shared_ptr<dcp::InteropSubtitleAsset> ass = dynamic_pointer_cast<dcp::InteropSubtitleAsset>(i->main_subtitle()->asset());
BOOST_REQUIRE (ass);
if (i->main_subtitle()) {
shared_ptr<dcp::InteropSubtitleAsset> ass = dynamic_pointer_cast<dcp::InteropSubtitleAsset>(i->main_subtitle()->asset());
BOOST_REQUIRE (ass);