f - add RouteNotFound error

Author: jkczyz

lightning/src/onion_message/messenger.rs

@@ -236,6 +236,8 @@ pub enum ResponseError {
 	GetNodeIdFailed,
 	/// No reply path in the onion message.
 	NoReplyPath,
+	/// Could not find a route to the destination.
+	RouteNotFound,
 	/// Failed to send the reply.
 	Sending(SendError),
 }
@@ -350,7 +352,16 @@ where
 			},
 		};
 
-		let intermediate_nodes = self.message_router.find_route(&sender, &destination);
+		let intermediate_nodes = match self.message_router.find_route(&sender, &destination) {
+			Some(intermediate_nodes) => intermediate_nodes,
+			None => {
+				log_info!(
+					self.logger, "No route to respond to onion message with path_id {:02x?}",
+					path_id
+				);
+				return error_handler.handle_response_error(ResponseError::RouteNotFound);
+			},
+		};
 
 		log_info!(self.logger, "Responding to onion message with path_id {:02x?}", path_id);