f debug_assert false unreachable non-existence

Author: dunxen

lightning/src/ln/channelmanager.rs

@@ -3567,8 +3567,12 @@ where
 			} else if let Some(channel) = peer_state.outbound_v1_channel_by_id.get_mut(channel_id) {
 				&mut channel.context
 			} else {
+				// This should not be reachable as we've already checked for non-existence in the previous channel_id loop.
+				debug_assert!(false);
 				return Err(APIError::ChannelUnavailable {
-					err: format!("Channel with ID {} was not found for the passed counterparty_node_id {}", log_bytes!(*channel_id), counterparty_node_id),
+					err: format!(
+						"Channel with ID {} for passed counterparty_node_id {} disappeared after we confirmed its existence - this should not be reachable!",
+						log_bytes!(*channel_id), counterparty_node_id),
 				});
 			};
 			let mut config = context.config();