cors_after_request dies if the request has headers=None

[dusktreader]

None is the default value of headers. If none are set, the following exception is raised:

Traceback (most recent call last):
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/app.py", line 1997, in __call__
    return self.wsgi_app(environ, start_response)
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/app.py", line 1985, in wsgi_app
    response = self.handle_exception(e)
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/app.py", line 1540, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/_compat.py", line 33, in reraise
    raise value
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/app.py", line 1982, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask/app.py", line 1614, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask_cors/extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/Users/tbeck/.virtualenvs/praetorian/lib/python3.6/site-packages/flask_cors/extension.py", line 173, in cors_after_request
    if resp.headers.get(ACL_ORIGIN):

This can happen with unhandled exceptions which cause a 500 error, or any response that does not set headers.

[ccrvlh]

Been having this problem on 3.0.8.
I think it started after I added health check api path, but don't understand exactly why.
My currently code for before_request and after_request is:

    # Log before request.
    @app.before_request
    def before():
        g.start = time.time()
        g.status = 0
        if request.endpoint == 'main.health_check':
            g.status = 1
            pass
        else:
            logger.debug(f'Received request to endpoint [{request.endpoint}], in blueprint [{request.blueprint}] and security [{request.is_secure}].')

    # Useful debugging interceptor to log all endpoint responses
    @app.after_request
    def after(response):
        if g.status == 1:
            pass
        else:
            now = time.time() 
            duration = round(now - g.start, 2)
            duration = time.localtime(duration)
            duration = str(duration[4]) + 'm:' + str(duration[5]) + 's'
            logger.debug(f'Finished request: [{response.status}], with [{response.data.decode("utf-8")}] and took [{duration}] seconds.')
            return response

And my health check route is:

@main.route('/api/health')
def health_check():
    return ''

Any ideas on what I might me doing wront?
Thanks.