Cannot set property 'article' of undefined

TypeError: Cannot set property 'article' of undefined
    at router.use (/var/www/meirui_frontend/source/routes/index.js:65:3)
    at Layer.handle [as handle_request] (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/layer.js:95:5)
    at trim_prefix (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:312:13)
    at /var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:280:7
    at Function.process_params (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:330:12)
    at next (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:271:10)
    at router.use (/var/www/meirui_frontend/source/routes/index.js:26:3)
    at Layer.handle [as handle_request] (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/layer.js:95:5)
    at trim_prefix (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:312:13)
    at /var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:280:7
    at Function.process_params (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:330:12)
    at next (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:271:10)
    at Function.handle (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:176:3)
    at router (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:46:12)
    at Layer.handle [as handle_request] (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/layer.js:95:5)
    at trim_prefix (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:312:13)
    at /var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:280:7
    at Function.process_params (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:330:12)
    at next (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:271:10)
    at app.use (/var/www/meirui_frontend/source/app.js:129:3)
    at Layer.handle [as handle_request] (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/layer.js:95:5)
    at trim_prefix (/var/www/meirui_frontend/source/node_modules/_express@4.13.4@express/lib/router/index.js:312:13)