Stop writing EcdsaChannelSigner

EcdsaChannelSigner is no longer deserialized as of version 0.0.113 and
downgrades before version 0.0.119 are no longer supported.

Author: jkczyz

lightning/src/chain/onchaintx.rs

@@ -33,7 +33,7 @@ use crate::chain::channelmonitor::{ANTI_REORG_DELAY, CLTV_SHARED_CLAIM_BUFFER};
 use crate::chain::package::{PackageSolvingData, PackageTemplate};
 use crate::chain::transaction::MaybeSignedTransaction;
 use crate::util::logger::Logger;
-use crate::util::ser::{Readable, ReadableArgs, MaybeReadable, UpgradableRequired, Writer, Writeable, VecWriter};
+use crate::util::ser::{Readable, ReadableArgs, MaybeReadable, UpgradableRequired, Writer, Writeable};
 
 use crate::io;
 use crate::prelude::*;
@@ -312,12 +312,9 @@ impl<ChannelSigner: WriteableEcdsaChannelSigner> OnchainTxHandler<ChannelSigner>
 
 		self.channel_transaction_parameters.write(writer)?;
 
-		let mut key_data = VecWriter(Vec::new());
-		self.signer.write(&mut key_data)?;
-		assert!(key_data.0.len() < core::usize::MAX);
-		assert!(key_data.0.len() < core::u32::MAX as usize);
-		(key_data.0.len() as u32).write(writer)?;
-		writer.write_all(&key_data.0[..])?;
+		// Write a zero-length signer. The data was no longer deserialized as of version 0.0.113 and
+		// downgrades before version 0.0.119 are no longer supported.
+		0u32.write(writer)?;
 
 		writer.write_all(&(self.pending_claim_requests.len() as u64).to_be_bytes())?;
 		for (ref ancestor_claim_txid, request) in self.pending_claim_requests.iter() {