Fix Node.js v14 compatibility by replacing ??= operator with equivalent if-null check

[Copilot]

• Fix Node.js v14 compatibility by replacing ??= operator with equivalent if-null check
• Update null check to use logical NOT operator (!barebonesLibSourceFile) instead of == null for consistency with codebase style

Closes #5008

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[sonarqubecloud]

Quality Gate passed

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1 Accepted issue

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