Financial-Times/o-colors — pull request #24 by jamesnicholls (2014-02-25 14:05:00+00:00)
Title: Inspect property before output to avoid sass choking on null values

See http://hugogiraudel.com/2014/01/27/casting-types-in-sass/#string. Inspect is only available in Sass 3.3; not sure if this is a problem