message: safe access to GetPointAtIdx(line, idx)
diff: @@ -255,9 +255,14 @@ inline bool CheckSForSegmentIntersection(Line l, float s) {
  return start_it != start_it_low;
  }
  -inline Point2d GetPointAtIdx(const Line& l, int idx) {
  +inline Point2d GetPointAtIdx(const Line& l, const uint idx) {
  + if (idx > l.obj_.size() - 1) {
  + LOG(WARNING) << "idx is outside line";
  + return l.obj_.back();
  + } else {
  return l.obj_.at(idx);
  }
  +}
  inline Point2d GetPointAtS(Line l, float s) {
  const size_t& length = l.obj_.size();
  