Fix nil constant

What does this MR do?

• Fix: fix printing of constant [] as [] rather than _Nil.
• Fix: fix constant [] node in C interpreter when used in ABC instructions (e.g. create_array_).

Changes to public APIs

None

Author's checklist (required)

• Intermediate commits compile (use git rebase -i main if not)
• Newly added code has a style consistent with the rest of the repository
• Newly added code is documented (guidelines)
• If bugs have been solved, tests have been added (guidelines)
• A changelog entry has been added (guidelines)

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