message: fix interUnitBonds parent check
diff: @@ -232,7 +232,9 @@ class Structure {
  get interUnitBonds() {
  if (this.state.interUnitBonds) return this.state.interUnitBonds;
  - if (this.parent && this.state.dynamicBonds === this.parent.state.dynamicBonds && this.parent.state.interUnitBonds?.edgeCount === 0) {
  + if (this.parent && this.state.dynamicBonds === this.parent.state.dynamicBonds &&
  + this.parent.state.interUnitBonds && this.parent.state.interUnitBonds.edgeCount === 0
  + ) {
  // no need to compute InterUnitBonds if parent's ones are empty
  this.state.interUnitBonds = new InterUnitBonds(new Map());
  } else {
  