add function getTypeLayer

include/robot_costmap_2d/unpreferred_layer.h

@@ -10,7 +10,10 @@ class UnPreferredLayer : public StaticLayer
 public:
   UnPreferredLayer();
   virtual ~UnPreferredLayer();
-
+  LayerType getType() const override
+  {
+      return LayerType::UNPREFERRED_LAYER;
+  }
 private:
   unsigned char interpretValue(unsigned char value);