Don't set sent_funding_txid in maybe_promote_splice_funding

When sending splice_locked, set PendingSplice::sent_funding_txid prior
to calling FundedChannel::maybe_promote_splice_funding. This makes the
latter idempotent when the splice is not promoted. Otherwise, successive
calls could override the previously set sent_funding_txid.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -9134,8 +9134,6 @@ where
 		debug_assert!(confirmed_funding_index < self.pending_funding.len());
 
 		let pending_splice = self.pending_splice.as_mut().unwrap();
-		pending_splice.sent_funding_txid = Some(splice_txid);
-
 		if pending_splice.sent_funding_txid == pending_splice.received_funding_txid {
 			log_info!(
 				logger,
@@ -9252,6 +9250,9 @@ where
 						}
 					}
 
+					let pending_splice = self.pending_splice.as_mut().unwrap();
+					pending_splice.sent_funding_txid = Some(splice_locked.splice_txid);
+
 					log_info!(
 						logger,
 						"Sending splice_locked txid {} to our peer for channel {}",
@@ -9420,6 +9421,9 @@ where
 			let pending_splice = self.pending_splice.as_ref().unwrap();
 			let funding = self.pending_funding.get(confirmed_funding_index).unwrap();
 			if let Some(splice_locked) = self.check_get_splice_locked(pending_splice, funding, height) {
+				let pending_splice = self.pending_splice.as_mut().unwrap();
+				pending_splice.sent_funding_txid = Some(splice_locked.splice_txid);
+
 				log_info!(logger, "Sending a splice_locked to our peer for channel {}", &self.context.channel_id);
 
 				let announcement_sigs = self