message: fix StructureElementSelectionManager.getPrincipalAxes for multiple entries
diff: @@ -83,7 +83,7 @@ class StructureElementSelectionManager {
  let offset = 0
  this.entries.forEach(v => {
  StructureElement.Loci.toPositionsArray(v.selection, positions, offset)
  - offset += StructureElement.Loci.size(v.selection)
  + offset += StructureElement.Loci.size(v.selection) * 3
  })
  return PrincipalAxes.ofPoints(Matrix.fromArray(positions, 3, elementCount))
  }
  