Titanium facebook module crash

I am developing a titanium IOS application which uses facebook module for facebook login. I am getting the following error when i close the fb module included window. Can anyone plz help? Thanx in advance.

Error log

[ERROR] :  The application has crashed with an uncaught exception 'NSInternalInconsistencyException'.
[ERROR] :  Reason:
[ERROR] :  An instance 0x17e8aa20 of class FBSessionManualTokenCachingStrategy was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x17d1bd30> (
[ERROR] :  <NSKeyValueObservance 0x17dc6850: Observer: 0x17e26170, Key path: accessToken, Options: <New: NO, Old: NO, Prior: YES> Context: 0x538bac, Property: 0x17de0f60>
[ERROR] :  <NSKeyValueObservance 0x17d110e0: Observer: 0x17e26170, Key path: expirationDate, Options: <New: NO, Old: NO, Prior: YES> Context: 0x538bac, Property: 0x17d1bd10>
[ERROR] :  )
[ERROR] :  Stack trace:
[ERROR] :  
[ERROR] :  0   CoreFoundation                      0x29ff549f <redacted> + 126
[ERROR] :  1   libobjc.A.dylib                     0x377abc8b objc_exception_throw + 38
[ERROR] :  2   CoreFoundation                      0x29ff53e5 <redacted> + 0
[ERROR] :  3   Foundation                          0x2ac9ec25 <redacted> + 288
[ERROR] :  4   libobjc.A.dylib                     0x377c5d5f <redacted> + 166
[ERROR] :  5   Qatar Tips                          0x0047130b Qatar Tips + 4375307
[ERROR] :  6   libobjc.A.dylib                     0x377c5d5f <redacted> + 166
[ERROR] :  7   Qatar Tips                          0x0046e3a5 Qatar Tips + 4363173
[ERROR] :  8   libobjc.A.dylib                     0x377c5d5f <redacted> + 166
[ERROR] :  9   Qatar Tips                          0x0006e76f Qatar Tips + 169839
[ERROR] :  10  libobjc.A.dylib                     0x377c5d5f <redacted> + 166
[ERROR] :  11  Qatar Tips                          0x0006cf71 Qatar Tips + 163697
[ERROR] :  12  Qatar Tips                          0x002ace57 Qatar Tips + 2522711
[ERROR] :  13  Qatar Tips                          0x0042b65f Qatar Tips + 4089439
[ERROR] :  14  Qatar Tips                          0x0042d4c9 Qatar Tips + 4097225
[ERROR] :  15  Qatar Tips                          0x00354cf7 Qatar Tips + 3210487
[ERROR] :  16  Qatar Tips                          0x00356bf5 Qatar Tips + 3218421
[ERROR] :  17  Qatar Tips                          0x00355acf Qatar Tips + 3214031
[ERROR] :  18  Qatar Tips                          0x00262927 Qatar Tips + 2218279
[ERROR] :  19  Qatar Tips                          0x0026256f Qatar Tips + 2217327
[ERROR] :  20  Qatar Tips                          0x002ab5d5 Qatar Tips + 2516437
[ERROR] :  21  Qatar Tips                          0x000659af Qatar Tips + 133551
[ERROR] :  22  Qatar Tips                          0x00067a8d Qatar Tips + 141965
[ERROR] :  23  Foundation                          0x2ad05b5b <redacted> + 1118
[ERROR] :  24  libsystem_pthread.dylib             0x37e6ee93 <redacted> + 138
[ERROR] :  25  libsystem_pthread.dylib             0x37e6ee07 _pthread_start + 118
[ERROR] :  26  libsystem_pthread.dylib             0x37e6cb90 thread_start + 8
[ERROR] :  *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'An instance 0x17e8aa20 of class FBSessionManualTokenCachingStrategy was deallocated while key value observers were still registered with it. Current observation info: <NSKeyValueObservationInfo 0x17d1bd30> (
[ERROR] :  <NSKeyValueObservance 0x17dc6850: Observer: 0x17e26170, Key path: accessToken, Options: <New: NO, Old: NO, Prior: YES> Context: 0x538bac, Property: 0x17de0f60>
[ERROR] :  <NSKeyValueObservance 0x17d110e0: Observer: 0x17e26170, Key path: expirationDate, Options: <New: NO, Old: NO, Prior: YES> Context: 0x538bac, Property: 0x17d1bd10>
[ERROR] :  )'
[ERROR] :  *** First throw call stack:
[ERROR] :  (0x29ff549f 0x377abc8b 0x29ff53e5 0x2ac9ec25 0x377c5d5f 0x47130b 0x377c5d5f 0x46e3a5 0x377c5d5f 0x6e76f 0x377c5d5f 0x6cf71 0x2ace57 0x42b65f 0x42d4c9 0x354cf7 0x356bf5 0x355acf 0x262927 0x26256f 0x2ab5d5 0x659af 0x67a8d 0x2ad05b5b 0x37e6ee93 0x37e6ee07 0x37e6cb90)

My window closing code

SubCategoryWindow.addEventListener('android:back', _androidBack);
function _androidBack(e) {
    bottomAdvertisementInterval = null;
    categoryId = null;
    SubCategoryWindow.removeEventListener('android:back', _androidBack);
    SubCategoryWindow.hide();
    SubCategoryWindow = null;
    LoadingIndicator = null;
    itemId = null;
    ImageCacheModule = null;
    fbShareBlob = null;
}