gulp使用了gulp-minify-css会报错?

Question

这是编译sass的代码:function sass() {  return gulp.src(['src/scss/{app,mall,datetime-picker,foundation-datepicker,style}.scss'])    .pipe($.sourcemaps.init())    .pipe($.sass({      includePaths: PATHS.sass    })      .on('error', $.sass.logError))    .pipe($.autoprefixer({      browsers: COMPATIBILITY    }))    // Comment in the pipe below to run UnCSS in production    //.pipe($.if(PRODUCTION, $.uncss(UNCSS_OPTIONS)))    .pipe($.if(PRODUCTION, $.cssnano()))    .pipe($.if(!PRODUCTION, $.sourcemaps.write()))    .pipe($.minifyCss())    .pipe(gulp.dest(PATHS.dist))    .pipe(browser.reload({ stream: true }));}没加.pipe($.minifyCss())的时候没报错