爆如下错误,这个是什么问题? node.js:201 throw e; // process.nextTick error, or ‘error’ event on first tick ^ TypeError: Cannot read property ‘length’ of null at Promise.<anonymous> (/data/home/htdocs/nodeclub/controllers/tag.js:125:13) at Promise.<anonymous> (/data/home/htdocs/nodeclub/node_modules/mongoose/lib/promise.js:120:8) at Promise.<anonymous> (events.js:67:17) at Promise.emit (/data/home/htdocs/nodeclub/node_modules/mongoose/lib/promise.js:59:38) at Promise.complete (/data/home/htdocs/nodeclub/node_modules/mongoose/lib/promise.js:70:20) at /data/home/htdocs/nodeclub/node_modules/mongoose/lib/query.js:876:30 at Array.0 (/data/home/htdocs/nodeclub/node_modules/mongoose/lib/utils.js:394:16) at EventEmitter._tickCallback (node.js:192:40)
谢谢~