#vulnerable code 
                                @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoadProfileMessage message) throws Exception {
        User authUser = Session.findUserByChannel(ctx.channel());

        String body = authUser.getUserProfile() == null ? "{}" : authUser.getUserProfile().toString();
        ctx.writeAndFlush(produce(message.id, message.command, body));
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    protected void channelRead0(ChannelHandlerContext ctx, LoadProfileMessage message) throws Exception {
        User authUser = Session.findUserByChannel(ctx.channel(), message.id);

        String body = authUser.getUserProfile() == null ? "{}" : authUser.getUserProfile().toString();
        ctx.writeAndFlush(produce(message.id, message.command, body));
    }