message: micro-optimize loop code
diff: @@ -548,7 +548,7 @@ class Slice {
  if (resolveExternals) {
  last = last.resolveExternal();
  }
  - while (begin != end) {
  + do {
  // fetch subattribute
  last = last.get(*begin);
  if (last.isExternal()) {
  @@ -558,7 +558,7 @@ class Slice {
  if (last.isNone() || (++begin != end && !last.isObject())) {
  return Slice();
  }
  - }
  + } while (begin != end);
  return last;
  }
  