我正在尝试将我的应用程序从React 15.6迁移到React 16.2，并且还将react-router-dom替换为react-router，但仍然有一些我不明白的错误。请帮我查一下。
index.js:12 Uncaught TypeError: Cannot read property 'initialize' of undefined
at Object.<anonymous> (index.js:12)
at __webpack_require__ (bootstrap 7e469d7f5710750b80d0:555)
at fn (bootstrap 7e469d7f5710750b80d0:86)
at Object.<anonymous> (bootstrap 7e469d7f5710750b80d0:578)
at __webpack_require__ (bootstrap 7e469d7f5710750b80d0:555)
at bootstrap 7e469d7f5710750b80d0:578
at bootstrap 7e469d7f5710750b80d0:578