Apoc Procedures can't return empty map

[MarkoZadravec]

BUG

Inside APOC procedures is a bug, that prevents you to return an empty map.
When returning empty map {} the APOC raise exception :

Expected positive int value, got 0

How to Reproduce the Problem

Create APOC procedure that returns an empty map :

CALL apoc.custom.asProcedure(
  'test',
  'RETURN {} AS res;',
  'write',
  [['res', 'map']],
  []
);

call custom.test;

returns:

Expected positive int value, got 0

Versions

• OS: mac and linux
• Neo4j: neo4j:4.4.6-community
• Neo4j-Apoc: apoc-4.4.0.3

[LampicJ15]

I have encountered the same issue running on Neo4j version 4.2.5-community / apoc 4.2.0.10
and on Neo4j version 4.1.6-community / apoc 4.1.0.9.