App crashes on OS X Yosemite due to NSOperation (QOS, Quality Of Service) - objective-c

Question

My application keeps crashing on OS X Yosemite for the following reason:
Crashed Thread: 7 Dispatch queue: NSOperationQueue 0x608000239d80 :: NSOperation 0x60000013b3a0 (QOS: UTILITY)
Changed my NSOperation to this:
if ([self respondsToSelector:#selector(qualityOfService)]) {
self.qualityOfService = NSQualityOfServiceUtility;
}
But application keeps crashing.
Stack trace of crashing thread:
Thread 7 Crashed:: Dispatch queue: NSOperationQueue 0x608000239d80 ::
NSOperation 0x60000013b3a0 (QOS: UTILITY)
0 libobjc.A.dylib 0x00007fff8af4f0dd objc_msgSend +
29
1 com.apple.CoreText 0x00007fff882d0ce7
TAttributes::ParseAttributes(__CFDictionary const*, void const*&,
TInlineVector, 30ul>&) + 521
2 com.apple.CoreText 0x00007fff882d06f9
TAttributes::TAttributes(__CFDictionary const*) + 257
3 com.apple.CoreText 0x00007fff882e8295
TRunEncoder::Encode(_CTGlyphStorage*, CFRange, unsigned int,
__CFDictionary const*) + 85
4 com.apple.CoreText 0x00007fff882e8231
CTRunCreateMutableRunsWithStorageAndOptions + 191
5 com.apple.UIFoundation 0x00007fff8f0f329e
-[NSATSGlyphStorage createCTTypesetter] + 705
6 com.apple.UIFoundation 0x00007fff8f0ecf0c
-[NSATSTypesetter _ctTypesetter] + 324
7 com.apple.UIFoundation 0x00007fff8f0f78b5
-[NSATSLineFragment layoutForStartingGlyphAtIndex:characterIndex:minPosition:maxPosition:lineFragmentRect:]
+ 89
8 com.apple.UIFoundation 0x00007fff8f0edd43
-[NSATSTypesetter _layoutLineFragmentStartingWithGlyphAtIndex:characterIndex:atPoint:renderingContext:]
+ 2901 9 com.apple.UIFoundation 0x00007fff8f0efa08 -[NSATSTypesetter layoutParagraphAtPoint:] + 156
10 com.apple.UIFoundation 0x00007fff8f040356 -[NSTypesetter
_layoutGlyphsInLayoutManager:startingAtGlyphIndex:maxNumberOfLineFragments:maxCharacterIndex:nextGlyphIndex:nextCharacterIndex:]
+ 4713
11 com.apple.UIFoundation 0x00007fff8f041ae5 -[NSTypesetter
layoutCharactersInRange:forLayoutManager:maximumNumberOfLineFragments:]
+ 246
12 com.apple.UIFoundation 0x00007fff8f0f0743
-[NSATSTypesetter layoutCharactersInRange:forLayoutManager:maximumNumberOfLineFragments:]
+ 967
13 com.apple.UIFoundation 0x00007fff8f0b9e76
-[NSLayoutManager(NSPrivate) _fillLayoutHoleForCharacterRange:desiredNumberOfLines:isSoft:] + 1334
14 com.apple.UIFoundation 0x00007fff8f0c370c
_NSFastFillAllLayoutHolesForGlyphRange + 1493
15 com.apple.UIFoundation 0x00007fff8f0c8e54
-[NSLayoutManager(NSPrivate) _drawBackgroundForGlyphRange:atPoint:] + 542
16 com.apple.AppKit 0x00007fff8f37fc15 -[NSTextView
drawRect:] + 1878
17 com.apple.AppKit 0x00007fff8f37f409
-[NSTextView(NSTextView_LayerBacking) drawLayer:inGraphicsContext:] + 493
18 com.apple.AppKit 0x00007fff8f332980
+[NSGraphicsContext configureGraphicsContextForCALayer:withCGContext:andRenderWithHandler:]
+ 97
19 com.apple.QuartzCore 0x00007fff92e70153
CABackingStoreUpdate_ + 3306
20 com.apple.QuartzCore 0x00007fff92e6f463
___ZN2CA5Layer8display_Ev_block_invoke + 59
21 com.apple.QuartzCore 0x00007fff92e6f41f
x_blame_allocations + 81
22 com.apple.QuartzCore 0x00007fff92e6ef1c
CA::Layer::display_() + 1546
23 com.apple.AppKit 0x00007fff8f31c89f
_NSBackingLayerDisplay + 617
24 com.apple.QuartzCore 0x00007fff92e6e641
CA::Layer::display_if_needed(CA::Transaction*) + 603
25 com.apple.QuartzCore 0x00007fff92e6dd7d
CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 35
26 com.apple.QuartzCore 0x00007fff92e6d50e
CA::Context::commit_transaction(CA::Transaction*) + 242
27 com.apple.QuartzCore 0x00007fff92e6d164
CA::Transaction::commit() + 390
28 com.apple.QuartzCore 0x00007fff92e7df55
CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned
long, void*) + 71
29 com.apple.CoreFoundation 0x00007fff902bdd87
CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23
30 com.apple.CoreFoundation 0x00007fff902bdce0
__CFRunLoopDoObservers + 368
31 com.apple.CoreFoundation 0x00007fff902af858
CFRunLoopRunSpecific + 328
32 com.apple.Foundation 0x00007fff8d04bab9
-[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 278
33 com.pack.MyApp 0x000000010ab54d5b -[SyncOperation
start] + 886
34 com.apple.Foundation 0x00007fff8cfe91a3 __NSOQSchedule_f
+ 184
35 libdispatch.dylib 0x00007fff925e9c13
_dispatch_client_callout + 8
36 libdispatch.dylib 0x00007fff925ed365
_dispatch_queue_drain + 1100
37 libdispatch.dylib 0x00007fff925eeecc
_dispatch_queue_invoke + 202
38 libdispatch.dylib 0x00007fff925ec6b7
_dispatch_root_queue_drain + 463
39 libdispatch.dylib 0x00007fff925fafe4
_dispatch_worker_thread3 + 91
40 libsystem_pthread.dylib 0x00007fff8596d6cb
_pthread_wqthread + 729
41 libsystem_pthread.dylib 0x00007fff8596b4a1 start_wqthread +
13
Thank you!