Bug due to handling of None value

[w158937299]

Agensgraph version: 2.13.0
Operating system: (Windows 11）
API/Driver: (psycopg2 2.9.7)
Steps to reproduce

As shown in this picture, this query first matches nodes connected to the 'u9' node with the type "nt0" and then returns the unique set of p2 property values for these nodes. The result returned by Neo4J is False, while Agensgraph returns False and None. This is because in Agensgraph, None indicates the absence, meaning that some nodes in the matched nodes may lack the p2 property, resulting in the presence of none. However, Distinct is meant to return unique elements, and after using distinct, None values should be removed to avoid potential user confusion.