`UPDATE` Onion failures without a `channel_update`

[TheBlueMatt]

I'm seeing some payment failures occasionally that come back with a full onion error of 10070000 (ie temporary_channel_failure with a channel_update len of 0). I've looked up a few of the nodes and those that have a node type tag on 1ml seem to say CLN. They might be an ancient version, no idea, one such node is https://1ml.com/node/020a1df50b701331a29782093210460b10eee0ac5ef6a01b9c51dff9b8fddf5fb0

I saw it testing some unique payments so it may be some bug on my end tickling CLN, dunno, but the spec seems to forbid this (Please note that the channel_update field is mandatory in messages whose failure_code includes the UPDATE flag).

[TheBlueMatt]

Apparently that specific node is running 22.11.1.