css - gulp-uncss 错误：无法解析：

Question

运行 gulp-uncss 以摆脱所有未使用的代码时遇到问题。该错误似乎与解析css有关。

C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\async.js:48
        fn = function () { throw arg; };
                           ^
 Error: uncss/node_modules/css: unable to parse undefined:
missing '{' near line 34:1
        29:        @import "components/_navbar";
        30:        @import "components/_slick";
        31:        @import "components/_slick-theme";
        32:        @import "components/_slack";
        33:        //@import "components/_landing";
        34:     ->

    at error (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:57:15)
    at declarations (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:214:25)
    at rule (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:481:21)
    at rules (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:103:56)
    at stylesheet (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:73:16)
    at Object.module.exports [as parse] (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\css\node_modules\css-parse\index.js:485:10)
    at process (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\src\uncss.js:158:22)
    at tryCatcher (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\util.js:11:23)
    at Promise._settlePromiseFromHandler (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:488:35)
    at Promise._settlePromise (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:548:18)
    at Promise._settlePromise0 (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:593:10)
    at Promise._settlePromises (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:676:18)
    at Promise._fulfill (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:617:18)
    at PromiseArray._resolve (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise_array.js:125:19)
    at PromiseArray._promiseFulfilled (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise_array.js:143:14)
    at Promise._settlePromise (C:\wamp64\www\css-cleanup\node_modules\gulp-uncss\node_modules\uncss\node_modules\bluebird\js\release\promise.js:553:26)

我的 gulpfile.js 看起来像这样：

var gulp = require('gulp');
var uncss = require('gulp-uncss');

gulp.task('default', function () {
    return gulp.src('sass/**/*.scss')
        .pipe(uncss({
            html: ['index.html']
        }))
        .pipe(gulp.dest('./css_new/'));
});