TypeError: E:\movie-master\app\views\pages\detail.jade:13
? ?11| ? ? ? ? ? .panel-body
? ?12| ? ? ? ? ? ? ul.media-list
?> 13| ? ? ? ? ? ? ? each item in comments
? ?14| ? ? ? ? ? ? ? ?li.media
? ?15| ? ? ? ? ? ? ? ? ?.pull-left
? ?16| ? ? ? ? ? ? ? ? ? ?a.comment(href="#comments", data-cid="#{item._id}", data-tid="#{item.from._id}")

Cannot read property 'length' of undefined
? ?at eval (eval at <anonymous> (E:\movie-master\node_modules\jade\lib\index.js:218:8), <anonymous>:467:31)
? ?at eval (eval at <anonymous> (E:\movie-master\node_modules\jade\lib\index.js:218:8), <anonymous>:876:4)
? ?at eval (eval at <anonymous> (E:\movie-master\node_modules\jade\lib\index.js:218:8), <anonymous>:1066:22)
? ?at res (E:\movie-master\node_modules\jade\lib\index.js:219:38)
? ?at Object.exports.renderFile (E:\movie-master\node_modules\jade\lib\index.js:380:38)
? ?at Object.exports.renderFile (E:\movie-master\node_modules\jade\lib\index.js:370:21)
? ?at View.exports.__express [as engine] (E:\movie-master\node_modules\jade\lib\index.js:417:11)
? ?at View.render (E:\movie-master\node_modules\express\lib\view.js:128:8)
? ?at tryRender (E:\movie-master\node_modules\express\lib\application.js:640:10)
? ?at EventEmitter.render (E:\movie-master\node_modules\express\lib\application.js:592:3)
? ?at ServerResponse.render (E:\movie-master\node_modules\express\lib\response.js:971:7)
? ?at E:\movie-master\app\controllers\movie.js:13:20
? ?at E:\movie-master\node_modules\mongoose\lib\query.js:2843:9
? ?at process._tickCallback (internal/process/next_tick.js:109:7)

這是為什么？？