ui: update lead's z position if modelV2 has been updated after startup. (#23355)

* model frame >= started_frame

* remove optional

selfdrive/ui/ui.cc

@@ -42,11 +42,11 @@ static int get_path_length_idx(const cereal::ModelDataV2::XYZTData::Reader &line
   return max_idx;
 }
 
-static void update_leads(UIState *s, const cereal::RadarState::Reader &radar_state, std::optional<cereal::ModelDataV2::XYZTData::Reader> line) {
+static void update_leads(UIState *s, const cereal::RadarState::Reader &radar_state, const cereal::ModelDataV2::XYZTData::Reader &line) {
   for (int i = 0; i < 2; ++i) {
     auto lead_data = (i == 0) ? radar_state.getLeadOne() : radar_state.getLeadTwo();
     if (lead_data.getStatus()) {
-      float z = line ? (*line).getZ()[get_path_length_idx(*line, lead_data.getDRel())] : 0.0;
+      float z = line.getZ()[get_path_length_idx(line, lead_data.getDRel())];
       calib_frame_to_full_frame(s, lead_data.getDRel(), -lead_data.getYRel(), z + 1.22, &s->scene.lead_vertices[i]);
     }
   }
@@ -110,12 +110,8 @@ static void update_state(UIState *s) {
   if (sm.updated("modelV2")) {
     update_model(s, sm["modelV2"].getModelV2());
   }
-  if (sm.updated("radarState")) {
-    std::optional<cereal::ModelDataV2::XYZTData::Reader> line;
-    if (sm.rcv_frame("modelV2") > 0) {
-      line = sm["modelV2"].getModelV2().getPosition();
-    }
-    update_leads(s, sm["radarState"].getRadarState(), line);
+  if (sm.updated("radarState") && sm.rcv_frame("modelV2") >= s->scene.started_frame) {
+    update_leads(s, sm["radarState"].getRadarState(), sm["modelV2"].getModelV2().getPosition());
   }
   if (sm.updated("liveCalibration")) {
     auto rpy_list = sm["liveCalibration"].getLiveCalibration().getRpyCalib();