Update code comment to explain why || is used instead of ??

Co-authored-by: Vinh Hoang <hoangzinh@users.noreply.github.com>

Author: MelvinBot

src/libs/TransactionUtils/index.ts

@@ -2144,6 +2144,7 @@ function getTaxName(policy: OnyxEntry<Policy>, transaction: OnyxEntry<Transactio
     // Only fall back to the default tax code when tax tracking is enabled on the policy.
     // When taxes are disabled and the user deletes a tax, taxCode becomes undefined (the API returns null, which Onyx strips).
     // Without this check, getTaxName would fall back to defaultTaxCode and display the default tax rate instead of showing empty.
+    // We use || instead of ?? because taxCode may be an empty string, which should also trigger the fallback.
     // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing
     const effectiveTaxCode = transaction?.taxCode || (policy?.tax?.trackingEnabled ? defaultTaxCode : undefined);
     const taxRate = effectiveTaxCode ? Object.values(transformedTaxRates(policy, transaction)).find((rate) => rate.code === effectiveTaxCode) : undefined;