input: Write a function to store and retrieve user data from a JSON file. The function should be able to store a dictionary containing user information and retrieve the stored data. If the JSON file does not exist or is empty, the function should handle the error appropriately.
  
  def store_user_data(data):
      with open('user_data.json', 'w') as f:
          json.dump(data, f)
  
  def get_user_data():
      try:
          with open('user_data.json') as f:
              return json.load(f)
      except FileNotFoundError:
          return None
  
  assert store_user_data({"Name": "John", "Age": 25, "City": "New York"})==None
  assert get_user_data()=={"Name": "John", "Age": 25, "City": "New York"}
  assert store_user_data({"Name": "Alice", "Age": 30, "City": "Los Angeles"})==None
  assert get_user_data()=={"Name": "Alice", "Age": 30, "City": "Los Angeles"}
  assert get_user_data()==None
  assert store_user_data({})==None
  assert get_user_data()=={}
output: def store_user_data(data):
      with open('user_data.json', 'w') as f:
          json.dump(data, f)
  
  def get_user_data():
      try:
          with open('user_data.json') as f:
              return json.load(f)
      except (FileNotFoundError, json.JSONDecodeError):
          return None