Failed to read register without entries (hash map)

[tatry]

When reading empty register (without entries, using hash map) psabpf-ctl tool returns error:

failed to build register JSON: Invalid argument

and exits with non-zero code.

---

Register definition:

struct nested {
	bit<16> nested_field;
}
struct type1 {
	bit<16> field0;
	nested nested_struct;
}
Register<type1, bit<64>>(10) reg;

Used command:

psabpf-ctl register get pipe 1 ingress_reg