Segfault on empty url()

[xzyfer]

body { 
  background: url()
}

LibSass 3.3.2

body {
  background: url(url(); }

LibSass 3.3.3

[1]    46392 segmentation fault  /Users/michael/Projects/Sass/sassc/bin/sassc test.scss

Ruby Sass

body {
  background: url(); }