message: fixed ihm mmcif parsing
diff: @@ -282,7 +282,7 @@ async function readIHM(ctx: RuntimeContext, format: mmCIF_Format, formatData: Fo
  const { ihm_model_list } = format.data;
  const entities: Entities = { data: format.data.entity, getEntityIndex: Column.createIndexer(format.data.entity.id) };
  - if (!format.data.atom_site.ihm_model_id.isDefined) {
  + if (format.data.atom_site._rowCount && !format.data.atom_site.ihm_model_id.isDefined) {
  throw new Error('expected _atom_site.ihm_model_id to be defined')
  }
  