Support Nullable Type for PolygonDictionary Attribute

Why it matters

This feature addresses the limitation of PolygonDictionary not handling Nullable attribute types, allowing users to represent optional polygon data. It improves flexibility in dictionary usage by supporting cases where polygon values can be missing or undefined.

How to use it

Users can define PolygonDictionary attributes with the Nullable type as usual in dictionary configuration files. The system will correctly process nullable polygon attributes without additional changes in queries or dictionary setup.