Can't Determine Reason for Crash from Xcode Crash Log - ios

Question

I had a user running my app on his iPhone 5. He performed a backup with iTunes. Bought a new iPhone 6S and restored from his iTunes backup.
When he launches my app it immediately crashes during launch. I got the crash logs from him, but there is no error message. It's crashing during the auto-generated -applicationDocumentsDirectory function in my AppDelegate.
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
Is there any way for me to determine what actually went wrong to see if it's something I can fix?
Incident Identifier: 3A0D56CA-EEAF-4F5A-8D16-D182E61034D5
CrashReporter Key: 9f4ce42b70e98d925f135c618394817f9451767b
Hardware Model: iPhone8,1
Process: MyApp [1198]
Path: /private/var/mobile/Containers/Bundle/Application/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXX/MyApp.app/MyApp
Identifier: com.inadaydevelopment.myapp
Version: 1.0.1 (1.0)
Code Type: ARM-64 (Native)
Parent Process: launchd [1]
Date/Time: 2015-10-02 14:30:25.25 -0700
Launch Time: 2015-10-02 14:30:25.25 -0700
OS Version: iOS 9.0.1 (13A405)
Report Version: 105
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Triggered by Thread: 0
Filtered syslog:
None found
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x000000019950b1e0 __pthread_kill + 8
1 libsystem_pthread.dylib 0x00000001995d4f0c pthread_kill + 112
2 libsystem_c.dylib 0x000000019947eb78 abort + 140
3 MyApp 0x000000010001ef7c -[AppDelegate applicationDocumentsDirectory] (AppDelegate.m:517)
4 MyApp 0x000000010001eae8 -[AppDelegate managedObjectContext] (AppDelegate.m:430)
5 MyApp 0x000000010002d004 -[BaseViewController awakeFromNib] (BaseViewController.m:54)
6 UIKit 0x00000001890e6058 -[UINib instantiateWithOwner:options:] + 2188
7 UIKit 0x0000000189324ea0 -[UIStoryboard instantiateViewControllerWithIdentifier:] + 196
8 UIKit 0x0000000189325000 -[UIStoryboard instantiateInitialViewController] + 68
9 UIKit 0x0000000188edd178 -[UIApplication _loadMainStoryboardFileNamed:bundle:] + 108
10 UIKit 0x0000000188caee40 -[UIApplication _loadMainInterfaceFile] + 264
11 UIKit 0x0000000188edc068 -[UIApplication _runWithMainScene:transitionContext:completion:] + 1316
12 UIKit 0x0000000188ed9300 -[UIApplication workspaceDidEndTransaction:] + 168
13 FrontBoardServices 0x000000018d7737ec -[FBSSerialQueue _performNext] + 184
14 FrontBoardServices 0x000000018d773b6c -[FBSSerialQueue _performNextFromRunLoopSource] + 56
15 CoreFoundation 0x000000018369c5a4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24
16 CoreFoundation 0x000000018369c038 __CFRunLoopDoSources0 + 540
17 CoreFoundation 0x0000000183699d38 __CFRunLoopRun + 724
18 CoreFoundation 0x00000001835c8dc0 CFRunLoopRunSpecific + 384
19 UIKit 0x0000000188ca80c8 -[UIApplication _run] + 460
20 UIKit 0x0000000188ca2f60 UIApplicationMain + 204
21 MyApp 0x000000010001bdd0 main (main.m:16)
22 libdyld.dylib 0x00000001993ee8b8 start + 4

Answer 1

Crashes without any useful stacktrace often happen when a message is sent to a deallocated instance. I struggled with this a few weeks ago when messing around with a UIViewController category.
Of course, you are right, a message sent to nil doesn't do no harm. A message sent to a deallocated instance of sth on the other hand leads to a crash.
Try turning ZombieObjects on, then you will get a log when this occurs, which can help you find the bug.