#vulnerable code 
                             public void execute() {
		try {
			server = service.listById(id);
			jedis = new Jedis(server.getHost(), Integer.parseInt(server
					.getPort()));
			if (commands.size() > 0) {
				RedisVersion version;
				if (serverVersion.containsKey(String.valueOf(id))) {
					version = serverVersion.get(String.valueOf(id));
				} else {
					version = getRedisVersion();
					serverVersion.put(String.valueOf(id), version);
				}

				getCommand(version).command();
			} else
				command();
			jedis.close();
		} catch (IOException e) {
			e.printStackTrace();
		}

	} 
                            #location 15 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             public void execute() {
		try {
			server = service.listById(id);
			jedis = new Jedis(server.getHost(), Integer.parseInt(server.getPort()));

			command();
			jedis.close();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}