fix warning

facontidavide · facontidavide · commit 727eb32017ab · 2020-03-23T17:02:11.000+01:00
diff --git a/include/behaviortree_cpp_v3/tree_node.h b/include/behaviortree_cpp_v3/tree_node.h
@@ -153,7 +153,7 @@ class TreeNode
     friend class BehaviorTreeFactory;
     friend class DecoratorNode;
     friend class ControlNode;
-    friend struct Tree;
+    friend class Tree;
 
     // Only BehaviorTreeFactory should call this
     void setRegistrationID(StringView ID)
