Brave Ads crash when fetching transaction history

[tmancey]

https://brave.sp.backtrace.io/p/brave/debug?time=all&filters=(_deleted%3D0%2C(callstack%2Cregex%2C%22(BatAds%7CAdsService%7CAdsImpl%7CConfirmationsImpl)%22)%2C(ver%2Cregex%2C%22(86.1%7C85.1%7C84.1%7C83.1)%22))&fingerprint=7e2f5be3d29aca65e1535f074da15f290c043c1049ac37db999e5ffe34eb0850

[00] logging::LogMessage::~LogMessage
[01] base::(anonymous namespace)::OnNoMemory
[02] std::__1::basic_string<char, std::__1::char_traits, std::__1::allocator >::basic_string
[03] ads::AdsImpl::GetUnredeemedTransactions
[04] ads::AdRewards::GetEstimatedPendingRewards
[05] ads::AdsImpl::GetTransactionHistory(std::__1::function<void
[06] bat_ads::BatAdsImpl::GetTransactionHistory(base::OnceCallback<void
[07] bat_ads::mojom::BatAdsStubDispatch::AcceptWithResponder
[08] bat_ads::mojom::BatAdsStub<mojo::UniquePtrImplRefTraits<bat_ads::mojom::BatAds, std::__1::default_delete<bat_ads::mojom::BatAds> > >::AcceptWithResponder
[09] mojo::InterfaceEndpointClient::HandleIncomingMessageThunk::Accept
[10] mojo::MessageDispatcher::Accept
[11] mojo::internal::MultiplexRouter::ProcessIncomingMessage
[12] mojo::internal::MultiplexRouter::Accept
[13] mojo::Connector::ReadAllAvailableMessages
[14] mojo::SimpleWatcher::OnHandleReady
[15] base::TaskAnnotator::RunTask
[16] base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWork
[17] base::MessagePumpDefault::Run
[18] base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::Run
[19] base::RunLoop::Run
[20] content::UtilityMain
[21] content::ContentMainRunnerImpl::Run
[22] service_manager::Main
[23] content::ContentMain
[24] ChromeMain

[tmancey]

@jsecretan Issue occurs if there are less transaction history entries than unblinded payment tokens. The only way I can see this is possible, is if users are editing confirmations.json

[btlechowski]

Verification passed on

Brave	1.17.59 Chromium: 86.0.4240.183 (Official Build) dev (64-bit)
Revision	0b568b034b8f7994697cb341eeca5979b84151cc-refs/branch-heads/4240@{#1374}
OS	Ubuntu 18.04 LTS

Verified test plan from brave/brave-core#6814
Used Virtual Box to slow down clients bandwidth http://www.virtualbox.org/manual/ch06.html#network_bandwidth_limit
Verified no crash.

Verification passed on

Brave	1.17.62 Chromium: 86.0.4240.185 (Official Build) dev (64-bit)
Revision	37e6f852ed18086458552039ad26421aa9fc7acc-refs/branch-heads/4240@{#1377}
OS	Windows 7 Service Pack 1 (Build 7601.24544)

Verified test plan from brave/brave-core#6814
Used Virtual Box to slow down clients bandwidth http://www.virtualbox.org/manual/ch06.html#network_bandwidth_limit
Verified no crash.

---

Verified passed with

Brave | 1.17.69 Chromium: 87.0.4280.60 (Official Build) (x86_64)
-- | --
Revision | 12697cfeb273d7de95cf9b18350d2c457f58224c-refs/branch-heads/4280@{#1352}
OS | macOS Version 10.14.6 (Build 18G6042)

Verified test plan from brave/brave-core#6814
Used Charles Proxy to throttle network.
No crash observed. Ran thru test plan 10+ times.