ext/requests - crashes when used with socket-io

[nirsky]

Describe your environment
Python 3.8.2
opentelemetry-sdk==0.6b0
opentelemetry-ext-http-requests==0.6b0 (was able to reproduce on 0.7.dev0 as well)
requests==2.23.0
python-socketio==4.5.1
python-socketio-client==1.1
websocket-client==0.57.0

Steps to reproduce
After enabling requests ext, like this:

http_requests.enable(trace_provider)

when using socketio client and connecting as follow:

import socketio

sio = socketio.Client()
sio.connect("socketio-server-url")

From this line of code (propagators.inject(type(headers).__setitem__, headers)), the following errors is thrown:
AttributeError("type object 'NoneType' has no attribute '__setitem__'")

This happens because for some reason the headers is None.
A possible fix will be adding if headers is not None: before calling the propagators.inject.

What is the expected behavior?
Expected to see the trace being sent.

What is the actual behavior?
app crashed.

Additional context
Happened on both 0.7.dev0 and 0.6b0 versions of the ext.

[Oberon00]

Technically, this looks like a bug in socket-io to me because headers is supposed to be a dict, not None (see https://github.com/python/typeshed/blob/545be37c4035d0df1a64fdeab08dbaec0f294bec/stdlib/3/urllib/request.pyi#L47 and https://docs.python.org/3/library/urllib.request.html#urllib.request.Request).
I guess we should both protect against None in ext/requests and file an issue at socket-io.

[github-actions]

This issue was marked stale due to lack of activity. It will be closed in 30 days.

[codeboten]

This was fixed in the requests instrumentation library.