fix(tracing): preserve empty block trace arrays

[Ri-go]

Return an allocated empty trace result slice for blocks without Ethereum transactions so JSON-RPC serializes [] instead of null, matching chain

Summary by CodeRabbit

• Bug Fixes
  • Improved block tracing behavior for blocks without Ethereum transactions.
  • Ensured tracing results remain consistently formatted when no transactions are present.

[coderabbitai]

📝 Walkthrough

Walkthrough

TraceBlock now passes a non-nil empty trace-result slice when a block contains no Ethereum transactions. All other tracing and caching behavior remains unchanged.

Changes

Trace result normalization

Layer / File(s)	Summary
Empty-transaction trace handling internal/evm/rpc/backend/tracing.go	The no-transaction path passes []*rpctypes.TxTraceResult{} instead of nil to the trace-result alignment helper.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Possibly related PRs

• InjectiveLabs/evm-gateway#8: Updates the same TraceBlock empty-result behavior and adds a corresponding test.

Suggested reviewers: maxim-inj

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the change to return allocated empty trace arrays for empty blocks.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/empty-trace-array

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