Proxito: check if attribute exists (#8220)

Ref https://sentry.io/organizations/read-the-docs/issues/2216431985/?environment=production&project=148442&query=is%3Aunresolved+host_project_slug&statsPeriod=14d

Author: stsewd

readthedocs/proxito/views/decorators.py

@@ -65,7 +65,7 @@ def inner_view(  # noqa
         if project is None:
             # Get a slug from the request if it can't be found in the URL
             if not project_slug:
-                project_slug = request.host_project_slug
+                project_slug = getattr(request, 'host_project_slug', None)
                 log.debug(
                     'Inserting project slug from request slug=[%s]',
                     project_slug