UNUSUAL plugin-cln-grpc: Failed to broadcast notification

### Issue and Steps to Reproduce
When running CLN 24.08.2 the logs are spammed with the below error:

```
2024-10-29T13:07:43-06:00 2024-10-29T19:07:43.412Z UNUSUAL plugin-cln-grpc: Failed to broadcast notification SendError(CustomMsg(CustomMsgNotification { payload: \"4c4fd1db5f7fe8f4073c7b226964223a226c6e6d6573736167653a6c69737470656572732364316462356637666538663430373363222c2272756e65223a226d6e545a746d6f31767a51777357393055654d30653436367369505653505665343739436f567038705841394d535a47623349675158427762476c6a595852706232346a222c226d6574686f64223a226c6973747065657273222c22706172616d73223a5b5d7d\", peer_id: PublicKey(73ad522549f8d8edc5b3a229bcd3306ce378ac9e7b5cd2010a572919a7b926bc01caa51f78eb5cfaa5e1e78ef017f94a50ca82fc28cb1d4c799f7bf6d77c0fba) }))
2024-10-29T13:07:43-06:00 2024-10-29T19:07:43.468Z UNUSUAL plugin-cln-grpc: Failed to broadcast notification SendError(CustomMsg(CustomMsgNotification { payload: \"4c4fd174d08a4b7552f87b226964223a226c6e6d6573736167653a676574696e666f2364313734643038613462373535326638222c2272756e65223a226d6e545a746d6f31767a51777357393055654d30653436367369505653505665343739436f567038705841394d535a47623349675158427762476c6a595852706232346a222c226d6574686f64223a22676574696e666f222c22706172616d73223a5b5d7d\", peer_id: PublicKey(73ad522549f8d8edc5b3a229bcd3306ce378ac9e7b5cd2010a572919a7b926bc01caa51f78eb5cfaa5e1e78ef017f94a50ca82fc28cb1d4c799f7bf6d77c0fba) }))
2024-10-29T13:07:43-06:00 2024-10-29T19:07:43.530Z UNUSUAL plugin-cln-grpc: Failed to broadcast notification SendError(CustomMsg(CustomMsgNotification { payload: \"4c4f3cd7f5f337158ac27b226964223a226c6e6d6573736167653a6c6973746f66666572732333636437663566333337313538616332222c2272756e65223a226d6e545a746d6f31767a51777357393055654d30653436367369505653505665343739436f567038705841394d535a47623349675158427762476c6a595852706232346a222c226d6574686f64223a226c6973746f6666657273222c22706172616d73223a5b5d7d\", peer_id: PublicKey(73ad522549f8d8edc5b3a229bcd3306ce378ac9e7b5cd2010a572919a7b926bc01caa51f78eb5cfaa5e1e78ef017f94a50ca82fc28cb1d4c799f7bf6d77c0fba) }))
```

This error is strange as this is a newly spun up node and I haven't connected to any peers yet. `listpeers` returns one peer (which presumably was automatically connected to bootstrap the graph?):

```
{
"peers": [
{
"id": "03bc26b9a71929570a01d25c7b9eac78e36c30d3bc29a2b3c5edd8f8492552ad73",
"connected": true,
"num_channels": 0,
"netaddr": [
"(ws)[::ffff:127.0.0.1]:54178"
],
"features": "0000000000000000"
}
]
}
```

### `getinfo` output
```
{
"id": "039e3a67dacaeb4ba2e196da59b786a7ce4e235ce86ee797470d3be1f2062ae0ff",
"alias": "start9-tc4qkiet8",
"color": "6044f2",
"num_peers": 1,
"num_pending_channels": 0,
"num_active_channels": 0,
"num_inactive_channels": 0,
"address": [
{
"type": "torv3",
"address": "gakguvacjxhdkqqdxc3zqxou6xyr36vmhxydxjh5xwr6e64al4m364yd.onion",
"port": 9735
}
],
"binding": [
{
"type": "ipv4",
"address": "0.0.0.0",
"port": 9735
}
],
"version": "v24.08.2",
"blockheight": 867967,
"network": "bitcoin",
"fees_collected_msat": 0,
"lightning-dir": "/root/.lightning/bitcoin",
"our_features": {
"init": "08a0800a8a59a1",
"node": "88a0800a8a59a1",
"channel": "",
"invoice": "02000002024100"
}
}
```

Aside from the errors in the logs, CLN seems otherwise healthy. Is is safe to assume this error is benign (as is generally the case with the `UNUSUAL plugin-...` errors?

### Environment
- CLN 24.08.2 running on StartOS 0.3.5~1