Fixed #2086 -- Changed `base.css` to import `null.css` (added in [6197]) instead of `null`.
Fixed #2086 -- Changed `base.css` to import `null.css` (added in [6197]) instead of `null`.


git-svn-id: 4f9f921b081c523744c7bf24d959a0db39629563@6716 bcc190cf-cafb-0310-a4f2-bffc1f526a37

FlaPer87/django-nonrel,FlaPer87/django-nonrel,aparo/django-nonrel,aparo/django-nonrel,FlaPer87/django-nonrel,aparo/django-nonrel