avoiding mutation

Author: weaverryan

lib/loaders/sass.js

@@ -37,7 +37,7 @@ module.exports = {
 
         sassLoaders.push({
             loader: 'sass-loader',
-            options: Object.assign(sassOptions, {
+            options: Object.assign({}, sassOptions, {
                 // needed by the resolve-url-loader
                 sourceMap: (true === webpackConfig.sassOptions.resolve_url_loader) || webpackConfig.useSourceMaps
             }),