cli: Placement bulding error looks unclear

[cthulhu-rider]

I formulated an a priori unenforceable network storage policy by making the number of replicas greater than the current number of nodes. I called neofs-cli container nodes command to check. Origin error was

not enough nodes to SELECT from: ''

While not enough nodes looks clear to me, selection part looks not, what empty string do we have here? I propose to clarify the case. Note that the error message is produces by NeoFS SDK Go lib.

P.S. the case can be spread to other CLI commands which build container placement.