json_node_export view not working as expected

https://cantusdatabase.org/chant/638264 is a chant created in OldCantus. We should be able to swap out `/chant/` and substitute `/json-node/` in order to view a json representation of the chant. Yet https://cantusdatabase.org/json-node/638264 gives us a 404.

On the 404 page, we see a brief error message: "Http404". In the view, we raise an `Http404` if the `id >= NODE_ID_CUTOFF`, and `NODE_ID_CUTOFF = 1_000_000`. The ID is not over 999_999, so I don't see why this should be being raised, but this could be where the error message is coming from.