NoneType object has no attribute put http meta

Using sdk version 2.4.2
```
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/exception.py", line 41, in inner
response = get_response(request)
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py", line 187, in _get_response
response = self.process_exception_by_middleware(e, request)
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py", line 227, in process_exception_by_middleware
response = middleware_method(request, exception)
File "/usr/local/lib/python2.7/dist-packages/aws_xray_sdk/ext/django/middleware.py", line 102, in process_exception
segment.put_http_meta(http.STATUS, 500)
AttributeError: 'NoneType' object has no attribute 'put_http_meta'
```