gulp-uglify error

help gulpnya error

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

gulp.task('js', function() {
	gulp.src('input.js')
		.pipe(uglify())
		.pipe(gulp.dest('assets'));
});

pesan errornya :

events.js:160 throw er; // Unhandled 'error' event ^ GulpUglifyError: unable to minify JavaScript at createError (C:\Users\Wandi\Desktop\enter\node_modules\gulp-uglify\lib\create-error.js:6:14) at wrapper (C:\Users\Wandi\Desktop\enter\node_modules\gulp-uglify\node_modules\lodash\_createHybrid.js:87:15) at trycatch (C:\Users\Wandi\Desktop\enter\node_modules\gulp-uglify\minifier.js:26:12) at DestroyableTransform.minify [as _transform] (C:\Users\Wandi\Desktop\enter\node_modules\gulp-uglify\minifier.js:76:19) at DestroyableTransform.Transform._read (C:\Users\Wandi\Desktop\enter\node_modules\through2\node_modules\readable-stream\lib\_stream_tra nsform.js:159:10) at DestroyableTransform.Transform._write (C:\Users\Wandi\Desktop\enter\node_modules\through2\node_modules\readable-stream\lib\_stream_tr ansform.js:147:83) at doWrite (C:\Users\Wandi\Desktop\enter\node_modules\through2\node_modules\readable-stream\lib\_stream_writable.js:347:64) at writeOrBuffer (C:\Users\Wandi\Desktop\enter\node_modules\through2\node_modules\readable-stream\lib\_stream_writable.js:336:5) at DestroyableTransform.Writable.write (C:\Users\Wandi\Desktop\enter\node_modules\through2\node_modules\readable-stream\lib\_stream_writ able.js:274:11) at write (C:\Users\Wandi\Desktop\enter\node_modules\vinyl-fs\node_modules\readable-stream\lib\_stream_readable.js:623:24)