Fix Raw Json Null Error

[rajatsingh23]

Closes #12932

What this PR does

Fixes an error that occurred when null was passed to persistField for RAW_JSON fields.

Changes made

• Removed unsafe persistField(null) call.
• Updated persistJsonField to safely parse JSON and skip invalid values.

Testing

• Manually tested clicking outside with empty and valid JSON.
• No error thrown, field saves only when JSON is valid.

Related

No related issue, minor internal improvement.

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[Devessier]

Thanks for your contribution, @rajatsingh23! I made a minor update to prevent persisting fields where specific logic has already been written for JSON fields.

[rajatsingh23]

@Devessier I'll make sure to handle such cases in the core logic in future PRs