planning: when perception message is not provided, keep planning

* but print an error message for every 10 seconds, incase the user
really forget to provide prediction message

modules/planning/planning.cc

@@ -96,7 +96,7 @@ Status Planning::Init() {
     return Status(ErrorCode::PLANNING_ERROR, error_msg);
   }
   if (FLAGS_enable_prediction && AdapterManager::GetPrediction() == nullptr) {
-    std::string error_msg("Prediction is not registered");
+    std::string error_msg("Enabled prediction, but no prediction not enabled");
     AERROR << error_msg;
     return Status(ErrorCode::PLANNING_ERROR, error_msg);
   }
@@ -232,16 +232,13 @@ void Planning::RunOnce() {
     return;
   }
 
-  // Update reference line provider
-  ReferenceLineProvider::instance()->UpdateVehicleState(vehicle_state);
-
   if (FLAGS_enable_prediction && AdapterManager::GetPrediction()->Empty()) {
-    not_ready->set_reason("prediction not ready");
-    AERROR << not_ready->reason() << "; skip the planning cycle.";
-    PublishPlanningPb(&not_ready_pb, start_timestamp);
-    return;
+    AERROR_EVERY(100) << "prediction is enabled but no prediction provided";
   }
 
+  // Update reference line provider
+  ReferenceLineProvider::instance()->UpdateVehicleState(vehicle_state);
+
   const double planning_cycle_time = 1.0 / FLAGS_planning_loop_rate;
   bool is_replan = false;
   const auto stitching_trajectory =