message: trace iterator fixes
diff: @@ -121,7 +121,7 @@ export class AtomicPolymerTraceIterator implements Iterator<PolymerTraceElement>
  private updateResidueSegmentRange(polymerSegment: Segmentation.Segment<number>) {
  const { index } = this.residueAtomSegments;
  this.residueSegmentMin = index[this.polymerRanges[polymerSegment.index * 2]];
  - this.residueSegmentMax = index[this.polymerRanges[polymerSegment.index * 2 + 1] - 1];
  + this.residueSegmentMax = index[this.polymerRanges[polymerSegment.index * 2 + 1]];
  }
  private getResidueIndex(residueIndex: number) {
  @@ -186,7 +186,7 @@ export class AtomicPolymerTraceIterator implements Iterator<PolymerTraceElement>
  const residueIndexBegPrev = this.getResidueIndex(residueIndexBeg - 1);
  this.currSecStrucType = residueIndexBeg === residueIndexBegPrev ? SecStrucTypeNA : this.getSecStruc(residueIndexBegPrev);
  this.nextSecStrucType = this.getSecStruc(residueIndexBeg);
  - this.currCoarseBackbone = false;
  + this.currCoarseBackbone = this.directionFromElementIndex[residueIndexBegPrev] === -1 || this.directionToElementIndex[residueIndexBegPrev] === -1;
  this.nextCoarseBackbone = this.directionFromElementIndex[residueIndexBeg] === -1 || this.directionToElementIndex[residueIndexBeg] === -1;
  break;
  }
  