title: AttributeError: 'NoneType' object has no attribute 'iterrows'
body: <p>I am trying to build a chatbot in rasa. But my class <strong>ActionSearchRestaurants</strong> is throwing this error:</p>
  
  <p>for index, row in resrnt.iterrows():
  AttributeError: 'NoneType' object has no attribute 'iterrows'</p>
  
  <p>Here is my class <strong>ActionSearchRestaurants</strong> that I'm using.</p>
  
  <pre><code>class ActionSearchRestaurants(Action):
      def name(self):
          return 'action_restaurant'
  
      def run(self, dispatcher, tracker, domain):
          config={ "user_key":"16cde****e0a12d10a7bc8bff6568031"}
          zomato = zomatopy.initialize_app(config)
          loc = tracker.get_slot('location')
          cuisine = tracker.get_slot('cuisine')
          location_detail=zomato.get_location(loc, 1)
  
          cols = ['restaurant_name', 'restaurant_address', 'avg_budget_for_two', 'zomato_rating']
          resrnt = pd.DataFrame(columns = cols)
  
          d1 = json.loads(location_detail)
          lat=d1["location_suggestions"][0]["latitude"]
          lon=d1["location_suggestions"][0]["longitude"]
          cuisines_dict={'bakery':5,'chinese':25,'cafe':30,'italian':55,'biryani':7,'north indian':50,'south indian':85}
          results=zomato.restaurant_search("", lat, lon, str(cuisines_dict.get(cuisine)), 10)
          d = json.loads(results)
          response=""
          if d['results_found'] == 0:
              response= "no results"
          else:
              for restaurant in d['restaurants']:
                  curr_res = {'zomato_rating':restaurant['restaurant']["user_rating"]["aggregate_rating"],'restaurant_name':restaurant['restaurant']['name'],'restaurant_address': restaurant['restaurant']['location']['address'], 'avg_budget_for_two': restaurant['restaurant']['average_cost_for_two']}
                  resrnt = resrnt.append(curr_res, ignore_index=True)
  
          resrnt=resrnt.sort_values(by=['zomato_rating'], ascending=False, inplace=True)
  
          for index, row in resrnt.iterrows():
                  response = response+ index + ". Found \""+ row['restaurant_name']+ "\" in "+ row['restaurant_address']+" has been rated "+ row['zomato_rating']+"\n"
  
          dispatcher.utter_message("-----"+ response)
          return [SlotSet('location',loc)]
  </code></pre>