sass/libsass — pull request #728 by xzyfer (2014-12-12 23:00:58+00:00)
Title: Error when trying to string concatenate with null

This PR brings the string concatenation behaviour in line with Ruby Sass by throwing an error when one of the strings involved is infact `null`.

Fixes https://github.com/sass/libsass/issues/698. Spec added https://github.com/sass/sass-spec/pull/168.