fix: render the 404 page for logged-in users

app_active and view_active read request.resolver_match, which is None
when no URL matched, so the navbar raised AttributeError and the 404
became a 500.

webvirtcloud/common_tags.py

@@ -7,12 +7,15 @@ register = template.Library()
 
 @register.simple_tag
 def app_active(request, app_name):
-    return "active" if request.resolver_match.app_name == app_name else ""
+    # resolver_match is None on error pages such as 404
+    match = request.resolver_match
+    return "active" if match and match.app_name == app_name else ""
 
 
 @register.simple_tag
 def view_active(request, view_name):
-    return "active" if request.resolver_match.view_name == view_name else ""
+    match = request.resolver_match
+    return "active" if match and match.view_name == view_name else ""
 
 
 @register.simple_tag

webvirtcloud/test_common_tags.py

@@ -0,0 +1,9 @@
+from django.contrib.auth import get_user_model
+from django.test import TestCase
+
+
+class NotFoundPageTestCase(TestCase):
+    def test_unknown_url_renders_404_for_logged_in_user(self):
+        user = get_user_model().objects.create_user("tags_user", "t@example.com", "pw")
+        self.client.force_login(user)
+        self.assertEqual(self.client.get("/no-such-page/").status_code, 404)