## What to do actually 500 error happens when access to a post that has the conditions below. - Exists. - Doesn't have publish_at parameter. It should show 404 error page. ``` Server Error happened! Request uri: https://www.mrrhp.com/ja/ravpower-20100-review HTTP_HOST: www.mrrhp.com HTTP_REFERER: https://www.mrrhp.com/admin/app/post/ HTTP_USER_AGENT: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36 QUERY_STRING: REMOTE_ADDR: 114.154.239.201 REQUEST_METHOD: GET Traceback (most recent call last): File "/env3.6/lib64/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner response = get_response(request) File "/env3.6/lib64/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response response = self.process_exception_by_middleware(e, request) File "/env3.6/lib64/python3.6/site-packages/django/core/handlers/base.py", line 124, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) File "/vagrant/app/views_lang.py", line 18, in post_ja return views.post(request, consts.Lang.JA, code) File "/vagrant/app/views.py", line 54, in post if post_bizlogic.is_available_post_obj(post_obj): File "/vagrant/app/bizlogic/post_bizlogic.py", line 22, in is_available_post_obj return post_obj.publish_at <= timezone.now() TypeError: '<=' not supported between instances of 'NoneType' and 'datetime.datetime' ```