What does this stack trace indicate? Crash caused by Xamarin.Media.MediaPicker.TakePhotoAsync on iOS8

What does this stack trace indicate? Crash caused by Xamarin.Media.MediaPicker.TakePhotoAsync on iOS8 on iPad2

I've logged a bug at... https://bugzilla.xamarin.com/show_bug.cgi?id=22853

But I'd like to make sure that it is not something I'm doing. It works fine on iOS7.

OS Version:          iOS 8.0 (12A365)
Report Version:      105

Exception Type:  EXC_BAD_ACCESS (SIGABRT)
Exception Subtype: KERN_INVALID_ADDRESS at 0x0000002c
Triggered by Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x3ab05dfc __pthread_kill + 8
1   libsystem_pthread.dylib         0x3ab85d0e pthread_kill + 58
2   libsystem_c.dylib               0x3aaa5934 abort + 72
3   TouchContainer                  0x00bd5b3a mono_handle_native_sigsegv (mini-exceptions.c:2360)
4   TouchContainer                  0x00bdef72 mono_sigsegv_signal_handler (mini.c:6868)
5   libsystem_platform.dylib        0x3ab800a0 _sigtramp + 40
6   UIKit                           0x30212304 _UIViewTopDownSubtreeTraversal + 260
7   UIKit                           0x30212304 _UIViewTopDownSubtreeTraversal + 260
8   UIKit                           0x305ab842 -[UIView(UIConstraintBasedLayout_EngineDelegate) _invalidateSystemLayoutSizeFittingSizeAtEngineDelegateLevel] + 118
9   UIKit                           0x300429c0 -[UIView(AdditionalLayoutSupport) _setNeedsUpdateConstraintsNeedingLayout:] + 68
10  UIKit                           0x305aa4e2 -[UIView(AdditionalLayoutSupport) _setSubviewWantsAutolayoutTripWantsAutolayout:] + 206
11  UIKit                           0x2ff88588 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 1352
12  UIKit                           0x2ff88032 -[UIView(Hierarchy) addSubview:] + 26
13  UIKit                           0x3024b2a2 __56-[UIPresentationController _transplantView:toSuperview:]_block_invoke + 242
14  UIKit                           0x3024af8c -[UIPresentationController _performBlockWithoutTriggeringResponderEvents:] + 96
15  UIKit                           0x3024b1a6 -[UIPresentationController _transplantView:toSuperview:] + 78
16  UIKit                           0x3024e474 __71-[UIPresentationController _initViewHierarchyForPresentationSuperview:]_block_invoke + 768
17  UIKit                           0x3024d358 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 148
18  UIKit                           0x2fffb916 _applyBlockToCFArrayCopiedToStack + 306
19  UIKit                           0x2ff777da _afterCACommitHandler + 454
20  CoreFoundation                  0x2caca842 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 18
21  CoreFoundation                  0x2cac7f24 __CFRunLoopDoObservers + 272
22  CoreFoundation                  0x2cac8326 __CFRunLoopRun + 910
23  CoreFoundation                  0x2ca15dac CFRunLoopRunSpecific + 472
24  CoreFoundation                  0x2ca15bbe CFRunLoopRunInMode + 102
25  GraphicsServices                0x33d4904c GSEventRunModal + 132
26  UIKit                           0x2ffe0efc UIApplicationMain + 1436
27  TouchContainer                  0x001d81ec wrapper_managed_to_native_MonoTouch_UIKit_UIApplication_UIApplicationMain_int_string___intptr_intptr + 268
28  TouchContainer                  0x0018533c MonoTouch_UIKit_UIApplication_Main_string___intptr_intptr (UIApplication.cs:122)
29  TouchContainer                  0x001852fc MonoTouch_UIKit_UIApplication_Main_string___string_string (UIApplication.cs:88)
30  TouchContainer                  0x000ad800 Touch_Container_Application_Main_string__ (MainClass.cs:84)
31  TouchContainer                  0x0036e9b4 wrapper_runtime_invoke_object_runtime_invoke_dynamic_intptr_intptr_intptr_intptr + 196
32  TouchContainer                  0x00be115c mono_jit_runtime_invoke (mini.c:6730)
33  TouchContainer                  0x00c2059a mono_runtime_invoke (object.c:2831)
34  TouchContainer                  0x00c242a2 mono_runtime_exec_main (object.c:4088)
35  TouchContainer                  0x00c240ea mono_runtime_run_main (object.c:3714)
36  TouchContainer                  0x00bcea74 mono_jit_exec (driver.g.c:1009)
37  TouchContainer                  0x00c59894 monotouch_main (monotouch-main.m:469)
38  TouchContainer                  0x00bb0da0 main (main.armv7.m:65)
39  TouchContainer                  0x000a9024 start + 36

It seems that what I was doing wrong was calling TakePhotoAsync from the Clicked event of an ActionSheet. The action sheet was still presented when the photo picker was presented. Pre iOS8 there must have been defensive code to silently work in this apparently illegal situation. The solution was to run the TakePhotoAsync in a BeginInvokeOnMainThread call. This queues the call on the main thread and allows the ActionSheet some space to finish closing.