Empty null value with line comment causes seg fault

[Mike Farah]

Describe the bug

This causes a segfault:

cat:
# comment

To Reproduce

https://go.dev/play/p/MNVPesMed_y

Expected behavior
Parses correctly with the comment

Version Variables

• Go version: 1.21
• go-yaml's Version: v1.11.2

Additional context