Question（提问）

TypeError: Cannot read property 'split' of null
    at required (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\requires-port\index.js:13:23)
    at Object.common.setupOutgoing (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\common.js:101:7)
    at Array.stream (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\passes\web-incoming.js:127:14)
    at ProxyServer.<anonymous> (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\index.js:81:21)
    at middleware (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy-middleware\lib\index.js:46:13)
    at handle (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\webpack-dev-server\lib\Server.js:318:18)
    at app.use (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\webpack-dev-server\lib\Server.js:326:47)
    at Layer.handle_error (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\layer.js:71:5)
    at trim_prefix (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:315:13)
    at C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:335:12)
    at next (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:275:10)
    at Layer.handle [as handle_request] (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\layer.js:97:5)
    at trim_prefix (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:317:13)
    at C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:335:12)
TypeError: Cannot read property 'split' of null
    at required (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\requires-port\index.js:13:23)
    at Object.common.setupOutgoing (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\common.js:101:7)
    at Array.stream (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\passes\web-incoming.js:127:14)
    at ProxyServer.<anonymous> (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy\lib\http-proxy\index.js:81:21)
    at middleware (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\http-proxy-middleware\lib\index.js:46:13)
    at handle (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\webpack-dev-server\lib\Server.js:318:18)
    at app.use (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\webpack-dev-server\lib\Server.js:326:47)
    at Layer.handle_error (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\layer.js:71:5)
    at trim_prefix (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:315:13)
    at C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:335:12)
    at next (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:275:10)
    at Layer.handle [as handle_request] (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\layer.js:97:5)
    at trim_prefix (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:317:13)
    at C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:284:7
    at Function.process_params (C:\Users\chenzw\IdeaProjects\otary-ui-manager\node_modules\express\lib\router\index.js:335:12)

Steps to reproduce（问题复现步骤）

vue.config.js 中的 devServer 配置项的before去除，就报错错了，不知如何解决