NSRangeException

Thread : Fatal Exception: NSRangeException
0  CoreFoundation                 0x0000000182c1259c __exceptionPreprocess + 132
1  libobjc.A.dylib                0x00000001933680e4 objc_exception_throw + 60
2  CoreFoundation                 0x0000000182afbc38 -[NSMutableArray sortUsingSelector:]
3  CoreFoundation                 0x0000000182b2279c -[NSArray sortedArrayFromRange:options:usingComparator:] + 284
4  MyApp                          0x000000010018ba24 __65-[ContactLoader loadContactsFromAllSourcesWithCompletion:]_block_invoke76 (ContactLoader.m:121)
5  Foundation                     0x0000000183aca58c __103+[__NSOperationInternal _observeValueForKeyPath:ofObject:changeKind:oldValue:newValue:indexes:context:]_block_invoke123 + 28
6  libdispatch.dylib              0x00000001939ad3ac _dispatch_call_block_and_release + 24
7  libdispatch.dylib              0x00000001939ad36c _dispatch_client_callout + 16
8  libdispatch.dylib              0x00000001939b940c _dispatch_root_queue_drain + 1152
9  libdispatch.dylib              0x00000001939ba75c _dispatch_worker_thread3 + 108
10 libsystem_pthread.dylib        0x0000000193b892e4 _pthread_wqthread + 816
11 libsystem_pthread.dylib        0x0000000193b88fa8 start_wqthread + 4