clean-css: TypeError: Cannot read property '0' of null

Hi,

I’m getting an error running v3.1.4 on my css. Attached the output of the error and css file. I’ve not been able to figure out what in the css is causing the issue and has only started happening since updating from an older version.

CSS file: https://www.dropbox.com/s/rdqrz5xx93ksbq5/app.css?dl=0

$ cleancss css/app.css --debug

Inlining local stylesheet: /facetalk/current/fci/css/app.css
Inlining local stylesheet: /facetalk/current/public/fci/fci-js/lib/jplayer/skin/blue.monday/jplayer.blue.monday.css

/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/properties/extractor.js:50
  return name.replace(/^\-\w+\-/, '').match(/([a-z]+)/)[0];
                                                       ^
TypeError: Cannot read property '0' of null
    at findNameRoot (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/properties/extractor.js:50:56)
    at extract (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/properties/extractor.js:20:22)
    at AdvancedOptimizer.restructure (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/selectors/optimizers/advanced.js:598:22)
    at _optimize (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/selectors/optimizers/advanced.js:729:12)
    at AdvancedOptimizer.optimize (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/selectors/optimizers/advanced.js:741:3)
    at SelectorsOptimizer.process (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/selectors/optimizer.js:15:55)
    at /facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/clean.js:174:31
    at run (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/clean.js:153:7)
    at minify (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/clean.js:165:3)
    at minifyWithDebug (/facetalk/current/fci/node_modules/grunt-contrib-cssmin/node_modules/clean-css/lib/clean.js:118:10)