Fix backwards compat for `blocked_monitor_updates`

In 1ce2beb77455a674888f3e3589723195eaa7b13c,
`Channel::blocked_monitor_updates` was moved to an even TLV to
ensure downgrades with vec entries are forbidden. However, the
serialized type remained `vec_type`, which is always written.

Instead, `optional_vec` must be used.

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 30280f0b1f131a45a883f7b292a2cc3cadbb0997..685819684803cd00d66fcf8c6bc821442d4c0678 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -6781,7 +6781,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Writeable for Channel<Signer> {
                        (5, self.context.config, required),
                        (6, serialized_holder_htlc_max_in_flight, option),
                        (7, self.context.shutdown_scriptpubkey, option),
-                       (8, self.context.blocked_monitor_updates, vec_type),
+                       (8, self.context.blocked_monitor_updates, optional_vec),
                        (9, self.context.target_closing_feerate_sats_per_kw, option),
                        (11, self.context.monitor_pending_finalized_fulfills, vec_type),
                        (13, self.context.channel_creation_height, required),
@@ -7089,7 +7089,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
                        (5, config, option), // Note that if none is provided we will *not* overwrite the existing one.
                        (6, holder_max_htlc_value_in_flight_msat, option),
                        (7, shutdown_scriptpubkey, option),
-                       (8, blocked_monitor_updates, vec_type),
+                       (8, blocked_monitor_updates, optional_vec),
                        (9, target_closing_feerate_sats_per_kw, option),
                        (11, monitor_pending_finalized_fulfills, vec_type),
                        (13, channel_creation_height, option),