Describe the bug
If you do not pass the "token" string after Bearer in Authorization header, it will result in an unhandled exception.

To Reproduce
Use django-oauth-toolkit and setup as a Django middleware.
Define any route and register in urls.py

Expected behavior

Version
3.0.1

Tested with

• I have tested with the latest published release and it's still a problem.
• I have tested with the master branch and it's still a problem.

Additional context
My request header looks like this:

I think problem is in here
It should check if there is space before splitting authheader by space.

Wondering, if you are expecting a PR.