Describe the bug
When parsing

test:

The lib turns this into

test: null

Note: I know that this is effectively what a blank value is - however I'm trying to keep as much formatting and comments as possible for roundtrip edits :)

To Reproduce
https://go.dev/play/p/74-SagRMZwO

Expected behavior

Keeps the actual null value used (blank)

Screenshots
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Version Variables

• Go version: [e.g. 1.21 ]
• go-yaml's Version: [e.g. v1.11.1 ]

Additional context
Add any other context about the problem here.