无法调用null错误的方法'insertBefore'

Question

我在使用ui-router的angularjs中收到此错误。我不知道是什么设置它，我无法追踪它。有没有人在此之前遇到过这个问题或对此有所了解？

我正在使用带有MEAN堆栈的yeoman（mongodb，express，angularjs，node.js）。我感觉错误在下面列出的states.js中。当错误开始出现时，这是我唯一一直在努力的事情。

TypeError: Cannot call method 'insertBefore' of null
    at http://localhost:9000/bower_components/angular/angular.js:3857:22
    at forEach (http://localhost:9000/bower_components/angular/angular.js:303:18)
at Object.enter (http://localhost:9000/bower_components/angular/angular.js:3856:9)
at http://localhost:9000/bower_components/angular/angular.js:18828:26
at publicLinkFn (http://localhost:9000/bower_components/angular/angular.js:5443:29)
at boundTranscludeFn (http://localhost:9000/bower_components/angular/angular.js:5555:21)
at controllersBoundTransclude (http://localhost:9000/bower_components/angular/angular.js:6145:18)
at ngRepeatAction (http://localhost:9000/bower_components/angular/angular.js:18826:15)
at Object.$watchCollectionAction (http://localhost:9000/bower_components/angular/angular.js:11347:11)
at Object.applyFunction [as fn] (<anonymous>:778:50) angular.js:9101

这是我的states.js

angular.module('lifeloggerApp', [
  'ngCookies',
  'ngResource',
  'ngSanitize',
  'ui',
  'ui.router'
])
  .config(function($stateProvider, $urlRouterProvider) {
$urlRouterProvider.otherwise("/Welcome");

$stateProvider
  .state('Welcome', {
    url: "/Welcome",
    templateUrl: "views/welcome.html"
  })
  .state('Welcome.About', {
    url: "/about",
    templateUrl: "views/about.html"
  })
  .state('Welcome.Contact', {
    url: "/contact",
    templateUrl: "views/contact.html"
  })
  .state('Welcome.Login', {
    url: "/login",
    templateUrl: "views/login.html"
  })
  .state('a', {
    url: "/a",
    views: {
      '': {
        templateUrl: "views/main.html",
        controller: 'MainCtrl'
      },
      'sidebar@a': {
        templateUrl: "views/sidebar.html"
      }
    }
  })
  .state('a.Dashboard', {
    url: "/dashboard",
    templateUrl: "views/dashboard.html"
  })
  .state('a.About', {
    url: "/about",
    templateUrl: "views/about.html"
  })
  .state('a.Contact', {
    url: "/contact",
    templateUrl: "views/contact.html"
  })
  .state('a.Profile', {
    abstract: true,
    url: "/profile",
    templateUrl: "views/profile.html"
  })
  .state('a.Profile.UserInfo', {
    url: "/userinfo",
    templateUrl: "views/profile.userinfo.html"
  })
  .state('a.Profile.EmailPref', {
    url: "/emailpref",
    templateUrl: "views/profile.emailpref.html"
  })
  .state('a.Profile.API', {
    url: "/api",
    templateUrl: "views/profile.api.html"
  })
  .state('a.Profile.Billing', {
    url: "/billing",
    templateUrl: "views/profile.billing.html"
  })
  .state('a.Profile.Settings', {
    url: "/settings",
    templateUrl: "views/profile.settings.html"
  })
$urlRouterProvider.when('/a/profile', '/a/profile/userinfo');
});