title: Kivy: 'NoneType' object has no attribute 'bind'
body: <p>I was testing out the ActionBar widget of Kivy, here is my program - </p>
  
  <pre><code> from kivy.app import App
   from kivy.lang import Builder
   from kivy.uix.boxlayout import BoxLayout
  
   Builder.load_string('''
   &lt;RootWidget&gt;:
        ActionBar:
            pos_hint: {'top':1}
        ActionView:
            ActionButton:
                text: "Button"
  ''')
  
  
  class RootWidget(BoxLayout):
       pass
  
  class MainApp(App):
       def build(self):
           return RootWidget()
  
  if __name__ == "__main__":
       MainApp().run()
  </code></pre>
  
  <p>Nothing much going on here, I just added an ActionBar inside the BoxLayout.<br>
  Here is the <a href="http://paste.ubuntu.com/11468078/" rel="nofollow">traceback</a> which I am getting on executing the program.</p>