Error: empty style element

```
root@30c7a47055f5:/tmp# node gulp-inline-css-demo1.js
Error: empty style element
at Object. (/tmp/node_modules/style-data/index.js:30:22)
at exports.each (/tmp/node_modules/cheerio/lib/api/traversing.js:293:24)
at module.exports (/tmp/node_modules/style-data/index.js:25:16)
at /tmp/node_modules/extract-css/index.js:14:9
at next (/tmp/node_modules/batch/index.js:118:7)
at Batch.end (/tmp/node_modules/batch/index.js:154:5)
at module.exports (/tmp/node_modules/extract-css/index.js:24:11)
at /tmp/node_modules/inline-css/lib/inlineContent.js:15:9
at tryCatcher (/tmp/node_modules/bluebird/js/main/util.js:26:23)
at Promise._resolveFromResolver (/tmp/node_modules/bluebird/js/main/promise.js:483:31)
at new Promise (/tmp/node_modules/bluebird/js/main/promise.js:71:37)
at inlineContent (/tmp/node_modules/inline-css/lib/inlineContent.js:8:12)
at /tmp/node_modules/inline-css/index.js:27:9
at tryCatcher (/tmp/node_modules/bluebird/js/main/util.js:26:23)
at Promise._resolveFromResolver (/tmp/node_modules/bluebird/js/main/promise.js:483:31)
at new Promise (/tmp/node_modules/bluebird/js/main/promise.js:71:37)
```

gulp-inline-css-demo1.js

```

const fs = require('fs');
const inlineCss = require('inline-css');

var options = {
xmlMode: true
};
options.url = 'file://./test-data/from-pdf2htmlex/geneve.html';

fs.readFile('./test-data/from-pdf2htmlex/geneve.html', 'utf8', (err, data) => {
inlineCss(data, options).then(html => {
fs.writeFile('./test-data/from-pdf2htmlex/index.html', html);
}).catch(function(reason) {
console.log(reason);
});
});
```

geneve.html
http://coolwanglu.github.io/pdf2htmlEX/demo/geneve.html