App crashes on iPhone 5 with iOS 6

The resolution center rejected my app because, as they say, it crashes on iPhone 5 with iOS 6.1.2.

I have an iPhone 4 with iOS 6.1.2 and it doesnt crash. I can't solve that problem!

They also wrote that the app crash when:

• 1. Launch the app
• 1. Login with Facebook.
• 1. App crashes when the device returns to the app.

Here the simbolicated crash log:

Last Exception Backtrace:
0   CoreFoundation                  0x344ec3e2 0x3442a000 + 795618
1   libobjc.A.dylib                 0x3c1dd95e 0x3c1d5000 + 35166
2   CoreFoundation                  0x344eff2c 0x3442a000 + 810796
3   CoreFoundation                  0x344ee648 0x3442a000 + 804424
4   CoreFoundation                  0x34446204 0x3442a000 + 115204
5   Kick - Serie A                  0x0007252c -[LetturaScrittura writeStringToFile:] (LetturaScrittura.m:26)
6   Kick - Serie A                  0x0006e9da __25-[Profilo carica_profilo]_block_invoke (Profilo.m:314)
7   Kick - Serie A                  0x0007e14a -[FBRequestConnection completeWithResults:orError:] (FBRequestConnection.m:1200)
8   Kick - Serie A                  0x0007d56c -[FBRequestConnection completeWithResponse:data:orError:] (FBRequestConnection.m:983)
9   Kick - Serie A                  0x0007b6aa __68-[FBRequestConnection startWithCacheIdentity:skipRoundtripIfCached:]_block_invoke_0 (FBRequestConnection.m:499)
10  Kick - Serie A                  0x0007f38e -[FBURLConnection invokeHandler:error:response:responseData:] (FBURLConnection.m:163)
11  Kick - Serie A                  0x0007f8f4 -[FBURLConnection connectionDidFinishLoading:] (FBURLConnection.m:233)
12  Foundation                      0x34e28910 0x34d53000 + 874768
13  Foundation                      0x34d68764 0x34d53000 + 87908
14  Foundation                      0x34d68680 0x34d53000 + 87680
15  CFNetwork                       0x341c964a 0x34141000 + 558666
16  CFNetwork                       0x341c8d2e 0x34141000 + 556334
17  CFNetwork                       0x341f100e 0x34141000 + 720910
18  CoreFoundation                  0x34432ac8 0x3442a000 + 35528
19  CFNetwork                       0x341f146e 0x34141000 + 722030
20  CFNetwork                       0x3415545c 0x34141000 + 83036
21  CoreFoundation                  0x344c18f2 0x3442a000 + 620786
22  CoreFoundation                  0x344c1158 0x3442a000 + 618840
23  CoreFoundation                  0x344bff2a 0x3442a000 + 614186
24  CoreFoundation                  0x34433238 0x3442a000 + 37432
25  CoreFoundation                  0x344330c4 0x3442a000 + 37060
26  GraphicsServices                0x38011336 0x3800c000 + 21302
27  UIKit                           0x3634f2b4 0x362f8000 + 357044
28  Kick - Serie A                  0x0006ac92 main (main.m:16)
29  libdyld.dylib                   0x3c60ab1c 0x3c609000 + 6940


Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x3c6d1350 __pthread_kill + 8
1   libsystem_c.dylib               0x3c647fb2 pthread_kill + 54
2   libsystem_c.dylib               0x3c684366 abort + 90
3   libc++abi.dylib                 0x3bc2cdda abort_message + 70
4   libc++abi.dylib                 0x3bc2a094 default_terminate() + 20
5   libobjc.A.dylib                 0x3c1dda58 _objc_terminate() + 144
6   libc++abi.dylib                 0x3bc2a118 safe_handler_caller(void (*)()) + 76
7   libc++abi.dylib                 0x3bc2a1b0 std::terminate() + 16
8   libc++abi.dylib                 0x3bc2b626 __cxa_rethrow + 90
9   libobjc.A.dylib                 0x3c1dd9b0 objc_exception_rethrow + 8
10  CoreFoundation                  0x3443329c CFRunLoopRunSpecific + 452
11  CoreFoundation                  0x344330c4 CFRunLoopRunInMode + 100
12  GraphicsServices                0x38011336 GSEventRunModal + 70
13  UIKit                           0x3634f2b4 UIApplicationMain + 1116
14  Kick - Serie A                  0x0006ac92 main (main.m:16)
15  libdyld.dylib                   0x3c60ab1c start + 0

Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0   libsystem_kernel.dylib          0x3c6c15d0 kevent64 + 24
1   libdispatch.dylib               0x3c5fcd22 _dispatch_mgr_invoke + 806
2   libdispatch.dylib               0x3c5f8374 _dispatch_mgr_thread + 32

Thread 2 name:  WebThread
Thread 2:
0   libsystem_kernel.dylib          0x3c6c0e30 mach_msg_trap + 20
1   libsystem_kernel.dylib          0x3c6c0fd0 mach_msg + 48
2   CoreFoundation                  0x344c12b6 __CFRunLoopServiceMachPort + 126
3   CoreFoundation                  0x344c002c __CFRunLoopRun + 900
4   CoreFoundation                  0x34433238 CFRunLoopRunSpecific + 352
5   CoreFoundation                  0x344330c4 CFRunLoopRunInMode + 100
6   WebCore                         0x3a432390 RunWebThread(void*) + 440
7   libsystem_c.dylib               0x3c62a0de _pthread_start + 306
8   libsystem_c.dylib               0x3c629fa4 thread_start + 4

Thread 3 name:  com.apple.NSURLConnectionLoader
Thread 3:
0   libsystem_kernel.dylib          0x3c6c0e30 mach_msg_trap + 20
1   libsystem_kernel.dylib          0x3c6c0fd0 mach_msg + 48
2   CoreFoundation                  0x344c12b6 __CFRunLoopServiceMachPort + 126
3   CoreFoundation                  0x344c002c __CFRunLoopRun + 900
4   CoreFoundation                  0x34433238 CFRunLoopRunSpecific + 352
5   CoreFoundation                  0x344330c4 CFRunLoopRunInMode + 100
6   Foundation                      0x34d80888 +[NSURLConnection(Loader) _resourceLoadLoop:] + 304
7   Foundation                      0x34e0422c __NSThread__main__ + 968
8   libsystem_c.dylib               0x3c62a0de _pthread_start + 306
9   libsystem_c.dylib               0x3c629fa4 thread_start + 4

Thread 4 name:  com.apple.CFSocket.private
Thread 4:
0   libsystem_kernel.dylib          0x3c6d1594 __select + 20
1   CoreFoundation                  0x344c5474 __CFSocketManager + 676
2   libsystem_c.dylib               0x3c62a0de _pthread_start + 306
3   libsystem_c.dylib               0x3c629fa4 thread_start + 4

Thread 5:
0   libsystem_kernel.dylib          0x3c6d1d98 __workq_kernreturn + 8
1   libsystem_c.dylib               0x3c61fad6 _pthread_workq_return + 14
2   libsystem_c.dylib               0x3c61f7f2 _pthread_wqthread + 362
3   libsystem_c.dylib               0x3c61f680 start_wqthread + 4

Thread 6:
0   libsystem_kernel.dylib          0x3c6d1d98 __workq_kernreturn + 8
1   libsystem_c.dylib               0x3c61fad6 _pthread_workq_return + 14
2   libsystem_c.dylib               0x3c61f7f2 _pthread_wqthread + 362
3   libsystem_c.dylib               0x3c61f680 start_wqthread + 4

Thread 0 crashed with ARM Thread State (32-bit):
    r0: 0x00000000    r1: 0x00000000      r2: 0x00000000      r3: 0x3e191524
    r4: 0x00000006    r5: 0x3e191b78      r6: 0x1dd85ca4      r7: 0x2fd979f4
    r8: 0x1dd85c80    r9: 0x00000300     r10: 0x00000000     r11: 0x3455b022
    ip: 0x00000148    sp: 0x2fd979e8      lr: 0x3c647fb7      pc: 0x3c6d1350
  cpsr: 0x00000010

Here's the LetturaScrittore method that makes the app crash (I use it to write on a .txt the email of the facebook user):

- (void)writeStringToFile:(NSString*)aString {

    // Build the path, and create if needed.
    NSString* filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString* fileName = @"myTextFile.txt";
    NSString* fileAtPath = [filePath stringByAppendingPathComponent:fileName];

    if (![[NSFileManager defaultManager] fileExistsAtPath:fileAtPath]) {
        [[NSFileManager defaultManager] createFileAtPath:fileAtPath contents:nil attributes:nil];
    }


    // The main act.
    [[aString dataUsingEncoding:NSUTF8StringEncoding] writeToFile:fileAtPath atomically:YES];
}

The reason for the crash is that you don't actually pass a NSString object to writeStringToFile.