TypeError: Invalid select() argument. Must be a string or object. at Query.select (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/mongoose/lib/query.js:1037:11) at Function.find (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/mongoose/lib/model.js:810:9) at Object.get_topics_by_query (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/controllers/topic.js:572:8) at /home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/controllers/site.js:58:13 at callbacks (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/lib/router/index.js:272:11) at param (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/lib/router/index.js:246:11) at pass (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/lib/router/index.js:253:5) at Router._dispatch (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/lib/router/index.js:280:4) at Object.handle (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/lib/router/index.js:45:10) at next (/home/admin/cnae/git/cnode-app-engine/apps_online/pingliwang/node_modules/express/node_modules/connect/lib/http.js:204:15)