Objective c dispatch_async crash

Question

code :

- (void)stopCurrentSessionFromSuite:(NSNotification*)notification{

        isCloseCurrentSession = YES;
        dispatch_async(self.dataSendingQueue, ^{
            CARD8 messageToDisableSession = rpcHostDisableMsg;
            [readerNwriter writeExact:(char*)&messageToDisableSession ofLenght:sizeof(CARD8) secApplied:NO];
        });
        [rpcCaptureMgr stopCaptureSession];

}

Crash :

Time Awake Since Boot: 1400 seconds

System Integrity Protection: enabled

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes:
KERN_INVALID_ADDRESS at 0x0000000000000070 Exception Note:
EXC_CORPSE_NOTIFY

Termination Signal: Segmentation fault: 11 Termination Reason:
Namespace SIGNAL, Code 0xb Terminating Process: exc handler [0]

VM Regions Near 0x70: --> __TEXT 000000010871a000-000000010873a000 [ 128K] r-x/rwx SM=COW /Applications/RemotePCSuite/*/RemotePCDesktop.app/Contents/MacOS/RemotePCDesktop

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread 0
libdispatch.dylib 0x00007fff72de50db _dispatch_continuation_async + 5 1 com.prosoftnet.remotepcDesktop 0x0000000108727fd5 -[RPCDesktopAppDelegate stopCurrentSessionFromSuite:] + 104 2 com.apple.CoreFoundation 0x00007fff4b7a333c CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER + 12 3 com.apple.CoreFoundation 0x00007fff4b7a32cf _CFXRegistrationPost_block_invoke + 63 4 com.apple.CoreFoundation 0x00007fff4b7ab92c __CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK + 12 5
com.apple.CoreFoundation 0x00007fff4b78e8a3 __CFRunLoopDoBlocks + 275 6 com.apple.CoreFoundation 0x00007fff4b78e668 __CFRunLoopRun + 3128 7 com.apple.CoreFoundation 0x00007fff4b78d797 CFRunLoopRunSpecific + 487 8 com.apple.HIToolbox 0x00007fff4aaa2866 RunCurrentEventLoopInMode + 286 9
com.apple.HIToolbox 0x00007fff4aaa25d6 ReceiveNextEventCommon + 613 10 com.apple.HIToolbox
0x00007fff4aaa2354 _BlockUntilNextEventMatchingListInModeWithFilter + 64 11 com.apple.AppKit 0x00007fff48d9fa23 _DPSNextEvent + 2085 12 com.apple.AppKit 0x00007fff49534e6c -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 3044 13 com.apple.AppKit 0x00007fff48d94831 -[NSApplication run] + 764 14 com.apple.AppKit 0x00007fff48d639d2 NSApplicationMain + 804 15 libdyld.dylib
0x00007fff72e0c145 start + 1