Add nil-element validation to flow data models

[zhangchiqing]

Add nil-element validation to more flow models: Hotstuff timeout, execution result, chunk data pack, block header, etc.

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[Copilot]

Pull request overview

This PR hardens Flow’s core data model constructors against malformed/untrusted inputs by adding validation that rejects nil elements (and nil nested pointers) inside otherwise non-nil container types. This reduces the risk of panics or inconsistent IDs when decoding network-provided payloads (e.g., CBOR null → Go nil).

Changes:

• Add nil-element checks for nested lists (e.g., ExecutionResult.Chunks) during payload/result construction.
• Validate nested pointer fields by reconstructing through constructors (e.g., HeaderBody.LastViewTC, HotStuff TimeoutObject.LastViewTC, ChunkDataPack.Collection).
• Extend unit tests to cover the new rejection paths.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
model/flow/payload.go	Rejects nil chunk entries within non-nil execution results in payloads.
model/flow/payload_test.go	Adds coverage for rejecting a payload containing a result with a nil chunk element.
model/flow/header.go	Validates LastViewTC via NewTimeoutCertificate instead of accepting nested nil pointers.
model/flow/header_test.go	Adds coverage for rejecting a header body with LastViewTC.NewestQC == nil.
model/flow/execution_result.go	Rejects nil chunk elements in ExecutionResult.Chunks.
model/flow/execution_result_test.go	Adds coverage for rejecting an execution result containing a nil chunk element.
model/flow/chunk.go	Validates optional Collection via NewCollection to reject nil transaction elements.
model/flow/chunk_test.go	Adds coverage for rejecting a chunk data pack whose collection contains a nil transaction.
model/flow/block_test.go	Updates block malleability test to account for stricter header-body validation.
consensus/hotstuff/model/timeout.go	Validates LastViewTC via flow.NewTimeoutCertificate and uses the validated TC for comparisons/return value.
consensus/hotstuff/model/timeout_test.go	Adjusts/extends tests to align with stricter TC validity requirements and new nil-nested-pointer rejection.

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[Copilot]

Updated in commit 0f35865765: TestBlockMalleability now passes the same block instance into RequireEntityNonMalleable, so the ParentView generator is consistent with the entity under test.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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