message: add back default value for ObjectIterator ctor
diff: @@ -220,7 +220,7 @@ class ObjectIterator {
  // The useSequentialIteration flag indicates whether or not the iteration
  // simply jumps from key/value pair to key/value pair without using the
  // index. The default `false` is to use the index if it is there.
  - explicit ObjectIterator(Slice slice, bool useSequentialIteration)
  + explicit ObjectIterator(Slice slice, bool useSequentialIteration = false)
  : _slice{slice}, _current{nullptr}, _size{0}, _position{0} {
  auto const head = slice.head();
  if (VELOCYPACK_UNLIKELY(slice.type(head) != ValueType::Object)) {
  