fix data race: addPlugin() and resizeMap() can be executed concurrently (#2512)

Co-authored-by: Kai-Tao Xie <kaitaoxie@qq.com>

Author: easylyou

nav2_costmap_2d/include/nav2_costmap_2d/layered_costmap.hpp

@@ -146,10 +146,8 @@ class LayeredCostmap
   /**
    * @brief Add a new plugin to the plugins vector to process
    */
-  void addPlugin(std::shared_ptr<Layer> plugin)
-  {
-    plugins_.push_back(plugin);
-  }
+  void addPlugin(std::shared_ptr<Layer> plugin);
+
 
   /**
    * @brief Add a new costmap filter plugin to the filters vector to process

nav2_costmap_2d/src/layered_costmap.cpp

@@ -89,6 +89,12 @@ LayeredCostmap::~LayeredCostmap()
   }
 }
 
+void LayeredCostmap::addPlugin(std::shared_ptr<Layer> plugin)
+{
+  std::unique_lock<Costmap2D::mutex_t> lock(*(combined_costmap_.getMutex()));
+  plugins_.push_back(plugin);
+}
+
 void LayeredCostmap::resizeMap(
   unsigned int size_x, unsigned int size_y, double resolution,
   double origin_x,