yss/grunt-tree — pull request #2 by enwin (2013-04-11 15:03:12+00:00)
Title: Compatibility fix for node 0.10.x

Since node 0.10 path.join() throws an exception for non string arguments.
http://nodejs.org/api/path.html#path_path_join_path1_path2

Patched the `toTree` method to filter non string `subdir`