How to solve Traceback AttributeError: 'NoneType' object has no attribute 'handle_text'

[peisong0109]

I met this problem when sending a text to Chatbot:

Traceback (most recent call last): File "/usr/local/lib/python3.6/dist-packages/RasaHost/services/conversations_service.py", line 89, in handle_text output = host.agent.handle_text(message, sender_id=sender_id) AttributeError: 'NoneType' object has no attribute 'handle_text'