startAccessingSecurityScopedResource Crash

I have gotten the following crash now two times in an app that is otherwise used a lot and is running fine:


Reason: -[NSNull startAccessingSecurityScopedResource]: unrecognized selector sent to instance 0x1f277c230

Stacktrace: (
	0   CoreFoundation                      0x000000019c48087c B37A1273-B0C2-312E-9E0B-7143FB645C69 + 968828
	1   libobjc.A.dylib                     0x000000019479fc00 objc_exception_throw + 60
	2   CoreFoundation                      0x000000019c51119c B37A1273-B0C2-312E-9E0B-7143FB645C69 + 1560988
	3   CoreFoundation                      0x000000019c3c5ff8 B37A1273-B0C2-312E-9E0B-7143FB645C69 + 204792
	4   CoreFoundation                      0x000000019c506b10 _CF_forwarding_prep_0 + 96
	5   UIKitCore                           0x000000019edae6a8 F1A8BD61-9CF2-3054-B622-CB63D6CEB4CB + 8349352
	6   QuickLook                           0x000000020ea213b4 D43C66FB-A39B-304E-A81B-8ADBFAAE2882 + 308148
	7   QuickLook                           0x000000020ea415bc D43C66FB-A39B-304E-A81B-8ADBFAAE2882 + 439740
	8   QuickLook                           0x000000020ea3ff38 D43C66FB-A39B-304E-A81B-8ADBFAAE2882 + 433976
	9   QuickLook                           0x000000020ea40378 D43C66FB-A39B-304E-A81B-8ADBFAAE2882 + 435064
	10  libdispatch.dylib                   0x00000001a434f6a8 89420547-98A3-352A-AD2B-BBCB6006FB29 + 9896
	11  libdispatch.dylib                   0x00000001a4351300 89420547-98A3-352A-AD2B-BBCB6006FB29 + 17152
	12  libdispatch.dylib                   0x00000001a435f998 89420547-98A3-352A-AD2B-BBCB6006FB29 + 76184
	13  libdispatch.dylib                   0x00000001a435f5b0 _dispatch_main_queue_callback_4CF + 44
	14  CoreFoundation                      0x000000019c3cb20c B37A1273-B0C2-312E-9E0B-7143FB645C69 + 225804
	15  CoreFoundation                      0x000000019c3c7f18 B37A1273-B0C2-312E-9E0B-7143FB645C69 + 212760
	16  CoreFoundation                      0x000000019c3c7668 CFRunLoopRunSpecific + 608
	17  GraphicsServices                    0x00000001df7925ec GSEventRunModal + 164
	18  UIKitCore                           0x000000019e7e42b4 F1A8BD61-9CF2-3054-B622-CB63D6CEB4CB + 2278068
	19  UIKitCore                           0x000000019e7e38f0 UIApplicationMain + 340
	20  MyApp                               0x0000000102c06280 MyApp + 483968
	21  dyld                                0x00000001bee1adcc A795AD37-6266-385E-95E6-C1CA804C926E + 24012
)

The symbol MyApp + 483968 just resolves to the main() function.

I'm not using this startAccessingSecurityScopedResource anywhere in my app. What could I do to debug this issue?