title: Error Vue.js "Cannot read property 'props' of undefined"
body: <p>Did everything on <a href="https://gorails.com/episodes/using-vuejs-for-nested-forms-part-1?autoplay=1" rel="noreferrer">gorails</a> tutorial, but something wrong.
  error message in Chrome:</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'props' of undefined   
      at normalizeProps (vue.runtime.esm.js?ff9b:1291)   
      at mergeOptions (vue.runtime.esm.js?ff9b:1363)   
      at mergeOptions (vue.runtime.esm.js?ff9b:1372)   
      at Vue$3.Vue._init (vue.runtime.esm.js?ff9b:4268)   
      at new Vue$3 (vue.runtime.esm.js?ff9b:4384)  
      at HTMLDocument.eval (hello_vue.js?94ab:29)     
      at Object.t.dispatch (turbolinks.self-)   
      at r.t.Controller.r.notifyApplicationAfterPageLoad ...)   
      at r.t.Controller.r.pageLoaded (t...)   
      at turbolinks.self...  
  </code></pre>
  
  <p>Hello_vue file:</p>
  
  <pre><code>import Vue from 'vue'
  import TurbolinksAdapter from "vue-turbolinks"
  import VueResource from "vue-resource"
  
  Vue.use(VueResource);
  
  document.addEventListener('turbolinks:load', () =&gt; {
  
      Vue.http.headers.common["X-CSRF-Token"] = document.querySelector('meta[name="csrf-token"]').getAttribute("content");
  
    var element = document.getElementById("team-form")
  
    if(element != null){
  
      var team = JSON.parse(element.dataset.team);
      var players_attributes = JSON.parse(element.dataset.playersAttributes);
      players_attributes.forEach(function(player){
          player._destroy = null  
      })
      team.players_attributes = players_attributes;
  
      var app = new Vue({
          el: element,
          mixins: [TurbolinksAdapter],
          data: function(){
              return { team: team }
          },
          methods: {
              addPlayer: function(){
                  team.players_attributes.push({
                  id: null,
                  name: "",
                  _destroy: null
                  })
              }
          }
      });
    }
  });
  </code></pre>
  
  <p>as I understand, an error in the initialization of the App object, but I can not understand in what exactly. I kind of did it right.</p>