#vulnerable code 
                             @Override
	public Flux<Payload> requestChannel(Payload payload, Publisher<Payload> payloads) {
		GatewayExchange exchange = GatewayExchange.fromPayload(REQUEST_CHANNEL, payload);
		Tags tags = getTags(exchange);
		Tags responderTags = tags.and("source", "responder");
		return findRSocketOrCreatePending(exchange)
				.flatMapMany(rSocket -> {
					Tags requesterTags = tags.and("source", "requester");
					Flux<Payload> flux = Flux.from(payloads)
							.doOnNext(s -> count("forward.request.channel.payload", requesterTags))
							.doOnError(t -> count("forward.request.channel.error", requesterTags))
							.doFinally(s -> count("forward.request.channel", requesterTags));

					if (rSocket instanceof ResponderRSocket) {
						ResponderRSocket socket = (ResponderRSocket) rSocket;
						return socket.requestChannel(payload, flux)
								.log(GatewayRSocket.class.getName()+".request-channel", Level.FINE);
					}
					return rSocket.requestChannel(flux);
				})
				.doOnNext(s -> count("forward.request.channel.payload", responderTags))
				.doOnError(t -> count("forward.request.channel.error", responderTags))
				.doFinally(s -> count("forward.request.channel", responderTags));
	} 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Override
	public Flux<Payload> requestChannel(Payload payload, Publisher<Payload> payloads) {
		GatewayExchange exchange = createExchange(REQUEST_CHANNEL, payload);
		Tags responderTags = Tags.of("source", "responder");
		return findRSocketOrCreatePending(exchange)
				.flatMapMany(rSocket -> {
					Tags requesterTags = Tags.of("source", "requester");
					Flux<Payload> flux = Flux.from(payloads)
							.doOnNext(s -> count(exchange, "payload", requesterTags))
							.doOnError(t -> count(exchange, "error", requesterTags))
							.doFinally(s -> count(exchange, requesterTags));

					if (rSocket instanceof ResponderRSocket) {
						ResponderRSocket socket = (ResponderRSocket) rSocket;
						return socket.requestChannel(payload, flux)
								.log(GatewayRSocket.class.getName()+".request-channel", Level.FINE);
					}
					return rSocket.requestChannel(flux);
				})
				.doOnNext(s -> count(exchange, "payload", responderTags))
				.doOnError(t -> count(exchange, "error", responderTags))
				.doFinally(s -> count(exchange, responderTags));
	}