React执行yarn start后显示空白页，求技术排查帮助

我是React新手，执行yarn start命令后应用显示空白页面。已尝试各类排查方案，甚至构建生产版本，仍未解决问题，恳请技术帮助。以下是我的App组件代码及控制台报错截图：

import { toast, ToastContainer } from 'react-toastify';
import React, { Component } from 'react';
import { Router, Route, Routes } from 'react-router-dom';
import './App.css';
import Home from './Components/Home/home';
import Profile from './Components/Profile/profile';
import SidePanel from './Components/SidePanel/sidePanel';
import SignIn from './Components/Signin/signin';
import Signup from './Components/Signup/Signup';


class App extends Component {
  showToast = (type, message) => {
    switch (type) {
      case 0:
        toast.warning(message)
        break;
      case 1:
        toast.success(message)
      default:
        break;
    }
  }
  render(props) {
    return (< Router >
      <ToastContainer
        autoClose={2000}
        hideProgressBar={true}
        position={toast.POSITION.TOP_CENTER}
      />
      <Routes>
        <Route
          exact
          path="/"
          render={prop => <Home {...props} />}
        />
        <Route
          path="/signin"
          render={prop => <SignIn showToast={this.showToast} {...props} />}
        />
        <Route
          path="/signup"
          render={prop => <Signup showToast={this.showToast} {...props} />}
        />
        <Route
          path="/profile"
          render={prop => <Profile showToast={this.showToast} {...props} />}
        />
        <Route
          path="/chat"
          render={prop => <SidePanel showToast={this.showToast} {...props} />}
        />
      </Routes>
    </Router>
    );
  };
};

export default App;

控制台报错截图：

内容的提问来源于stack exchange，提问作者Sam Zack