main.css is not being generated

[ghost]

When I run grunt build --verbose I am getting the following when the cssmin task is run

Running "cssmin:generated" (cssmin) task
Verifying property cssmin.generated exists in config...OK
Files: bower_components/foundation/css/foundation.css, bower_components/normalize.css/normalize.css -> dist/styles/vendor.css
Files: [no src] -> dist/styles/main.css
Options: report="min"
Reading bower_components/foundation/css/foundation.css...OK
Reading bower_components/normalize.css/normalize.css...OK
Writing dist/styles/vendor.css...OK
File dist/styles/vendor.css created: 194.3 kB → 138.61 kB
>> Destination not written because minified CSS was empty.

So the result is that there is no main.css being generated. Why is this happening?

Here is a Gist containing my Gruntfile.js :
https://gist.github.com/3lfist/86f1cc3076e01ef5a905

and here is my index.html which contains the usemin blocks
https://gist.github.com/3lfist/c39eedeb7c8ef6adae48

[gracegimon]

did you manage to fix this?