dash.exceptions.InvalidIndexException after upgrading Dash #641

I have build an app which was running smoothly in Dash-0.28.5. After I upgraded Dash from 0.28.5 to 0.39.0, I encounter the error by running the same App.

File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 2309, in call
return self.wsgi_app(environ, start_response)
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask_compat.py", line 35, in reraise
raise value
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask_compat.py", line 35, in reraise
raise value
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\flask\app.py", line 1799, in dispatch_request
return self.view_functionsrule.endpoint
File "C:\Users\dongxushao\AppData\Local\Continuum\anaconda3\lib\site-packages\dash\dash.py", line 570, in index
pl=plural
dash.exceptions.InvalidIndexException: Missing element new DashRenderer in index.