f clarify upstream -> 0.1 diff

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -13872,6 +13872,7 @@ where
 			// payments. This avoids edge-cases around MPP payments resulting in redundant actions.
 			for (_, monitor) in args.channel_monitors.iter() {
 				let counterparty_opt = outpoint_to_peer.get(&monitor.get_funding_txo().0);
+				// outpoint_to_peer missing the funding outpoint implies the channel is closed
 				if counterparty_opt.is_none() {
 					for (htlc_source, (htlc, _)) in monitor.get_pending_or_resolved_outbound_htlcs() {
 						let logger = WithChannelMonitor::from(&args.logger, monitor, Some(htlc.payment_hash));