joomla/joomla-cms — pull request #719 by rvsjoen (2013-02-14 13:00:37+00:00)
Title: Template manager spits out errors when there is no css folder in the root of the template

"JFolder: files: Path is not a folder. Path [...]/css

No need to create errors for templates which do not have a css directory so instead just check if it is a directory or not.