fix(sentry#6931306293): fix issue with url context resolver

[JacobCoffee]

Description

• When browsing somewhere nonexistent we crash and throw a Sentry error:
  https://www.python.org/search/?q=about&page=45 leads to:

which fails loading JS and the title bar is also funky:

---

(InteractiveConsole)
>>> from django.test import RequestFactory
>>> 
>>> from pydotorg import context_processors
>>> 
>>>   factory = RequestFactory()
  File "<console>", line 1
    factory = RequestFactory()
IndentationError: unexpected indent
>>> factory = RequestFactory()
>>> request = factory.get('/this-does-not-exist/')
>>> result = context_processors.url_name(request)
>>> print(result)
{'URL_NAMESPACE': None, 'URL_NAME': None}
>>> request = factory.get('/about/')
>>> result = context_processors.url_name(request)
>>> 
>>> print(result)
{'URL_NAMESPACE': '', 'URL_NAME': 'about'}
>>> 

testing locally we get the right context:

Closes

• Fixes AttributeError: 'NoneType' object has no attribute 'engine' #2792