message: fix seq number in sequence widget for atomic models without auth_seq_id
diff: @@ -132,7 +132,10 @@ export class Sequence<P extends SequenceProps> extends PluginUIComponent<P> {
  const l = StructureElement.Loci.getFirstLocation(loci, this.location);
  if (l) {
  if (Unit.isAtomic(l.unit)) {
  - const seqId = StructureProperties.residue.auth_seq_id(l)
  + const { residues } = l.unit.model.atomicHierarchy
  + const seqId = residues.auth_seq_id.isDefined
  + ? StructureProperties.residue.auth_seq_id(l)
  + : StructureProperties.residue.label_seq_id(l)
  const insCode = StructureProperties.residue.pdbx_PDB_ins_code(l)
  sequenceNumber = `${seqId}${insCode ? insCode : ''}`
  } else if (Unit.isCoarse(l.unit)) {
  