uniapp中使用 vant，运行到真机基座出现报错Cannot read property 'userAgent' of undefined

[suolong182]

使用的是若依的移动端框架+vant2+vau2，在浏览器运行没有问题不会报错，选择运行到真机时，出现报错，报错信息如下：
reportJSException >>>> exception function:createInstanceContext, exception:white screen cause create instanceContext failed,check js stack ->Uncaught TypeError: Cannot read property 'userAgent' of undefined
at isIOS (app-service.js:14002:69)
at (app-service.js:13970:31)
at webpack_require (app-service.js:80:30)
at (app-service.js:13377:20)
at webpack_require (app-service.js:80:30)
at (app-service.js:11488:37)
at webpack_require (app-service.js:80:30)
at (app-service.js:9268:43)
at webpack_require (app-service.js:80:30)
at eval (:11:36)

qing'wen请问是什么原因导致的？求解，谢谢！