feat: allow projections to union with null (no-op)

[romain-gilliotte]

Definition of Done

General

• Write an explicit title for the Pull Request, following Conventional Commits specification
• Test manually the implemented changes
• Validate the code quality (indentation, syntax, style, simplicity, readability)
• Ensure that Types have been updated according to your changes (if needed)

Security

• Consider the security impact of the changes made