TypeError: object NoneType can't be used in 'await' expression

[gaodianzhuo]

功能正常运行就是报个错误

In [2]: import pywebio

In [3]: pywebio.version
Out[3]: '1.2.3'

python3.8 chat_room.py
Listen on 0.0.0.0:8080
ERROR:tornado.application:Uncaught exception GET /?app=index&session=NEW (::1)
HTTPServerRequest(protocol='http', host='localhost:8080', method='GET', uri='/?app=index&session=NEW', version='HTTP/1.1', remote_ip='::1')
Traceback (most recent call last):
File "/home/arthur/.local/lib/python3.8/site-packages/tornado/web.py", line 1592, in _execute
result = yield result
File "/home/arthur/.local/lib/python3.8/site-packages/tornado/gen.py", line 1133, in run
value = future.result()
File "/home/arthur/.local/lib/python3.8/site-packages/pywebio/platform/tornado.py", line 106, in get
await super().get()
TypeError: object NoneType can't be used in 'await' expression