Fixed #29775 -- Fixed URL converters in a nested namespaced path.

When using include() without namespaces of some urlpatterns that
have an include() with namespace, the converters of the parent
include() weren't being used to convert the arguments of reverse().

tests/urlpatterns/path_base64_urls.py

@@ -4,8 +4,16 @@ from . import converters, views
 
 register_converter(converters.Base64Converter, 'base64')
 
+subsubpatterns = [
+    path('<base64:last_value>/', views.empty_view, name='subsubpattern-base64'),
+]
+
 subpatterns = [
     path('<base64:value>/', views.empty_view, name='subpattern-base64'),
+    path(
+        '<base64:value>/',
+        include((subsubpatterns, 'second-layer-namespaced-base64'), 'instance-ns-base64')
+    ),
 ]
 
 urlpatterns = [