refactor: make Note Fields non-null

[david-allison]

Kotlin Cleanup, useful for Kotlin conversion of ParsedNode

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[lukstbit]

LGTM