refactor: avoid Object.assign

Author: evilebottnawi

lib/index.js

@@ -40,7 +40,7 @@ const SyntaxError = require('./Error')
  * @return {cb} cb      Result
  */
 module.exports = function loader (css, map, meta) {
-  const options = Object.assign({}, loaderUtils.getOptions(this))
+  const options = loaderUtils.getOptions(this) || {};
 
   validateOptions(require('./options.json'), options, 'PostCSS Loader')