chore: resolve undefined-field

lua/nvim-tree/renderer/decorator/modified.lua

@@ -4,6 +4,7 @@ local HL_POSITION = require("nvim-tree.enum").HL_POSITION
 local ICON_PLACEMENT = require("nvim-tree.enum").ICON_PLACEMENT
 
 local Decorator = require("nvim-tree.renderer.decorator")
+local DirectoryNode = require("nvim-tree.node.directory")
 
 ---@class (exact) DecoratorModified: Decorator
 ---@field icon HighlightedString|nil
@@ -55,7 +56,7 @@ function DecoratorModified:calculate_highlight(node)
     return nil
   end
 
-  if node.nodes then
+  if node:is(DirectoryNode) then
     return "NvimTreeModifiedFolderHL"
   else
     return "NvimTreeModifiedFileHL"