fix: Add null check

[pratikmankawde]

High Level Overview of Change

Add a missing null check after txRead() in iteratePriceData() (GetAggregatePrice.cpp), preventing a potential nullptr dereference.

Context of Change

iteratePriceData() walks the chain of previous transactions that modified a PriceOracle ledger object. At line 72, it calls ledger->txRead(prevTx).second to get the transaction metadata, then immediately dereferences it on the next line (meta->getFieldArray(sfAffectedNodes)) without checking for null.

This is inconsistent with every other txRead call site in the codebase, which all check for null before dereferencing. If txRead returns a null metadata pointer, this would be a nullptr dereference / crash.

Triggering conditions: The bug cannot be triggered remotely on a node with consistent data. The sfPreviousTxnID field is maintained by the transaction engine and always points to a real transaction. For txRead to return null, the ledger would need to exist but not contain the referenced transaction — which requires pre-existing local data corruption (SHAMap structural corruption, transaction engine bug, or incomplete ledger reconstruction).

The fix adds a null guard that returns early, matching the existing defensive pattern used throughout the function.

API Impact

No API impact. This is a defensive null check — behavior is unchanged for nodes with consistent data.

Test Plan

Existing GetAggregatePrice_test passes (no behavioral change for valid data paths)
Code inspection confirms the fix matches the defensive pattern used at other txRead call sites in the codebase

[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.1%. Comparing base (afcf6fb) to head (7c01370).

Files with missing lines	Patch %	Lines
...xrpld/rpc/handlers/orderbook/GetAggregatePrice.cpp	66.7%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #7305     +/-   ##
=========================================
- Coverage     82.1%   82.1%   -0.0%     
=========================================
  Files         1011    1011             
  Lines        76343   76345      +2     
  Branches      7417    7412      -5     
=========================================
- Hits         62691   62683      -8     
- Misses       13652   13662     +10     

Files with missing lines	Coverage Δ
...xrpld/rpc/handlers/orderbook/GetAggregatePrice.cpp	98.8% <66.7%> (-0.6%)	⬇️

... and 6 files with indirect coverage changes

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[Copilot]

Pull request overview

This PR adds a defensive null check in iteratePriceData() to avoid dereferencing a null transaction metadata pointer returned by txRead(), improving robustness in the presence of unexpected ledger inconsistencies (e.g., local corruption) without changing behavior on valid data paths.

Changes:

• Add a nullptr guard after ledger->txRead(prevTx).second before accessing sfAffectedNodes.
• Simplify the metadata pointer type declaration by using std::shared_ptr<STObject const> directly.

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