Fix error message

Signed-off-by: anhnv3991 <anh.nguyen.2@tier4.jp>

Author: anhnv3991

localization/ndt_scan_matcher/src/map_update_module.cpp

@@ -32,9 +32,12 @@ MapUpdateModule::MapUpdateModule(
   secondary_ndt_ptr_.reset(new NdtType);
 
   if (ndt_ptr_) {
-      RCLCPP_ERROR_STREAM_THROTTLE(logger_, *clock_, 1000, "Attempt to update a null NDT pointer.");
     *secondary_ndt_ptr_ = *ndt_ptr_;
   }
+  else
+  {
+    RCLCPP_ERROR_STREAM_THROTTLE(logger_, *clock_, 1000, "Attempt to update a null NDT pointer.");
+  }
 
   // Initially, a direct map update on ndt_ptr_ is needed.
   // ndt_ptr_'s mutex is locked until it is fully rebuilt.