background crashes clean-css

[vmarkovtsev]

shrthnd seems to mess up background in some cases.

How I test

fs = require('fs');
fs.readFile('bootstrap.css', 'utf8', function (err,data) {
  var source = data;
  var shrthnd = require('shrthnd');
  source = shrthnd(source).string;
  var cleancss = require('clean-css');
  var minified = new cleancss().minify(source).styles;
});

Reduced test case

Part of Bootstrap 3.3.4.

.progress-striped .progress-bar,
.progress-bar-striped {
  background-image: -webkit-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:      -o-linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  background-image:         linear-gradient(45deg, rgba(255, 255, 255, .15) 25%, transparent 25%, transparent 50%, rgba(255, 255, 255, .15) 50%, rgba(255, 255, 255, .15) 75%, transparent 75%, transparent);
  -webkit-background-size: 40px 40px;
          background-size: 40px 40px;
}

Occuring error

/tmp/shrthnd/node_modules/clean-css/lib/properties/validator.js:135
      if (s.indexOf('/') < 0)
           ^
TypeError: Cannot read property 'indexOf' of undefined
    at Object.module.exports.validator.isValidBackgroundPositionAndSize (/tmp/shrthnd/node_modules/clean-css/lib/properties/validator.js:135:12)
    at module.exports.breakUp.background (/tmp/shrthnd/node_modules/clean-css/lib/properties/processable.js:239:28)
    at Object.breakUp (/tmp/shrthnd/node_modules/clean-css/lib/properties/processable.js:153:25)
    at Token.tokenizeOne (/tmp/shrthnd/node_modules/clean-css/lib/properties/token.js:93:47)
    at Array.map (native)
    at Function.Token.tokenize (/tmp/shrthnd/node_modules/clean-css/lib/properties/token.js:105:26)
    at Optimizer.compact (/tmp/shrthnd/node_modules/clean-css/lib/properties/optimizer.js:258:24)
    at Object.Optimizer.process (/tmp/shrthnd/node_modules/clean-css/lib/properties/optimizer.js:274:9)
    at optimizeProperties (/tmp/shrthnd/node_modules/clean-css/lib/selectors/optimizers/advanced.js:711:27)
    at _optimize (/tmp/shrthnd/node_modules/clean-css/lib/selectors/optimizers/advanced.js:730:5)

shrthnd output

.progress-striped .progress-bar,
.progress-bar-striped {
  background: linear-gradient(45deg, rgba(255, 255, 255, .15) 25% 0 0/40px 40px, transparent 25% 0 0/40px 40px, transparent 50% 0 0/40px 40px, rgba(255, 255, 255, .15) 50% 0 0/40px 40px, rgba(255, 255, 255, .15) 75% 0 0/40px 40px, transparent 75% 0 0/40px 40px, transparent) 0 0/40px 40px;
  -webkit-background-size: 40px 40px;
}

[wottpal]

Same issue here