Random Xamarin crash / ios7 / StoreKit - xamarin.ios

Question

We are currently facing a very annoying critical random crash with our in-app purchases process.
Random because only some customers encounter this issue.
The crash suddenly appears with ios7 release (before ios7 RTM, no crash reports were received). So we suppose it is related to a change in StoreKit behavior.
It seems that we have an issue when we call the transaction.OriginalTransaction
Do other Xamarin users are facing the same issue?
Searching Xamarin forum / Google and so on, we have found that our issue could perhaps be related to this bug we found here https://bugzilla.xamarin.com/show_bug.cgi?id=2871#c13
Does someone found a workaround to this random bug ?
More generally (without Xamarin/Monotouch involved), is someone facing a similar issue with ios7 and storekit?
We are using :
Xamarin Studio 4.2.1 (build 1)
Xamarin.iOS 7.0.4.209
Mono 3.2.4
Xcode 4.6.3
Here is our code for the UpdatedTransactions method:
public override void UpdatedTransactions(SKPaymentQueue queue, SKPaymentTransaction[] transactions)
{
List<SKPaymentTransaction> chartTransactions = new List<SKPaymentTransaction>();
foreach (SKPaymentTransaction transaction in transactions)
{
string productId = transaction.TransactionState == SKPaymentTransactionState.Restored ? transaction.OriginalTransaction.Payment.ProductIdentifier : transaction.Payment.ProductIdentifier;
if (string.IsNullOrEmpty(_ProductIdPrefix) == false && productId.StartsWith(_ProductIdPrefix, true, CultureInfo.InvariantCulture))
{
chartTransactions.Add(transaction);
}
}
_PaymentTransactionChangedCallback(chartTransactions.ToArray());
}
Here is the re-symbolicated crash log (we have resymbolized many customers crash-log with the same call stack) :
...
(not re-symbolized)
...
mono_handle_native_sigsegv (in OurAppMono) (mini-exceptions.c:2325)
sigabrt_signal_handler (in OurAppMono) (mini-posix.c:196)
...
(not re-symbolized)
...
monotouch_unhandled_exception_handler (in OurAppMono) (monotouch-glue.m:1440)
mono_invoke_unhandled_exception_hook (in OurAppMono) (mini-exceptions.c:2561)
mono_thread_abort (in OurAppMono) (mini.c:2629)
mono_handle_exception_internal (in OurAppMono) + 2136
mono_handle_exception (in OurAppMono) (mini-exceptions.c:1902)
handle_signal_exception (in OurAppMono) (exceptions-arm.c:559)
<--
MonoTouch_StoreKit_SKPaymentTransaction_get_OriginalTransaction (in OurAppMono) + 48
-->
wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr (in OurAppMono) + 196
mono_jit_runtime_invoke (in OurAppMono) (mini.c:5793)
mono_runtime_invoke (in OurAppMono) (object.c:2790)
native_to_managed_trampoline_OurApp_ChartsServer_IOSChartPaymentObserver_UpdatedTransactions (in OurAppMono) (<stdin>:1214)
...
(not re-symbolized)
...
wrapper_managed_to_native_MonoTouch_UIKit_UIApplication_UIApplicationMain_int_string___intptr_intptr (in OurAppMono) + 236
OurAppMono_Application_Main_string__ (in OurAppMono) + 164
wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr (in OurAppMono) + 196
mono_jit_runtime_invoke (in OurAppMono) (mini.c:5793)
mono_runtime_invoke (in OurAppMono) (object.c:2790)
mono_runtime_exec_main (in OurAppMono) (object.c:3972)
mono_runtime_run_main (in OurAppMono) (object.c:3602)
mono_jit_exec (in OurAppMono) (driver.c:1125)
main (in OurAppMono) (main.m:482)
Edit:
the crash seems to be linked to ios7.
(not related with Xamarin).
The solution is to handle (productid = nil) returned by the AppStore and to Finish matching transactions.
Cf.:
Following in app purchase, app crashing on startup. productIdentifier=nil?
In App Purchase (IAP) process appears to be crashing the app on launch for one of my users

Answer 1

I do not think this is related to bug #2871, but I believe it is instead a NullReferenceException inside the OriginalTransaction getter (or around where you call the OriginalTransaction getter - exact location might be a bit off due to optimizations).
The app is crashing because you're not handling the exception - I suggest you add exception handling to your UpdateTransaction method, and handle the exception somehow (send a log back to yourself for instance, error message to the user and/or try again, etc.)