It hasn't been clarified, although if you don't have a list spot, you obviously can't have them, and you always have enough picks at the back end of the draft to fill your list.What happens if you don't have another pick (or list spot). IE you use your last pick to select another player (because no bid has come) and then there is a bid.
But I haven't seen any announced rules about a situation where nobody has bid in the 4th round, and you decide to take another player with the aim of taking your FS/NGA/academy player as a rookie.
Convention is that nobody bids that late, but I'm not sure there is a rule about it yet.
They also haven't announced anything about being able to live trade picks after a bid post 37, although logic would suggest that this won't be allowed.