check builder output instead of input size

Signed-off-by: mitukou1109 <mitukou1109@gmail.com>

Author: mitukou1109

planning/autoware_path_generator/src/utils.cpp

@@ -460,13 +460,6 @@ std::vector<geometry_msgs::msg::Point> crop_line_string(
   const std::vector<geometry_msgs::msg::Point> & line_string, const double s_start,
   const double s_end)
 {
-  if (line_string.size() < 2) {
-    RCLCPP_WARN(
-      rclcpp::get_logger("path_generator").get_child("utils").get_child(__func__),
-      "Input line string has less than 2 points, returning input as is");
-    return line_string;
-  }
-
   if (s_start < 0.) {
     RCLCPP_WARN(
       rclcpp::get_logger("path_generator").get_child("utils").get_child(__func__),
@@ -484,6 +477,10 @@ std::vector<geometry_msgs::msg::Point> crop_line_string(
   auto trajectory = autoware::trajectory::Trajectory<geometry_msgs::msg::Point>::Builder()
                       .set_xy_interpolator<trajectory::interpolator::Linear>()
                       .build(line_string);
+  if (!trajectory) {
+    return {};
+  }
+
   trajectory->crop(s_start, s_end - s_start);
   return trajectory->restore();
 }