title: Crittercism says Can't add self as subview as the reason with NSInvalidArgumentException
body: <p>Can't figure out from stack trace , the code snippet where crash is happening but from breadcrumbs it happens at various places. Not just one. What could be the reason for the same?    </p>
  
  <pre><code>Crashed Thread
  0   CoreFoundation 0x30c1aecb __exceptionPreprocess + 131
  1   libobjc.A.dylib 0x3b3b5ce7 objc_exception_throw + 36
  2   CoreFoundation 0x30c1ae0d +[NSException raise:format:] + 110
  3   UIKit 0x33457ae5 -[UIView(Internal) _addSubview:positioned:relativeTo:] + 106
  4   UIKit 0x33457a73 -[UIView(Hierarchy) addSubview:] + 28
  5   UIKit 0x336208bd __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke + 1194
  6   UIKit 0x3345e0b5 +[UIView(Animation) performWithoutAnimation:] + 70
  7   UIKit 0x336201cd -[_UINavigationParallaxTransition animateTransition:] + 730
  8   UIKit 0x335dd3b1 -[UINavigationController _startCustomTransition:] + 2614
  9   UIKit 0x334fa46f -[UINavigationController _startDeferredTransitionIfNeeded:] + 416
  10  UIKit 0x334fa279 -[UINavigationController __viewWillLayoutSubviews] + 42
  11  UIKit 0x334fa211 -[UILayoutContainerView layoutSubviews] + 182
  12  UIKit 0x3344c2e5 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 378
  13  QuartzCore 0x330c831b -[CALayer layoutSublayers] + 140
  14  QuartzCore 0x330c3b3f _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 348
  15  QuartzCore 0x330c39d1 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE +    14
  16  QuartzCore 0x330c33e5 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 226
  17  QuartzCore 0x330c31f7 _ZN2CA11Transaction6commitEv + 312
  18  UIKit 0x3344f99f _UIApplicationHandleEventQueue + 8268
  19  CoreFoundation 0x30be5faf __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 12
  20  CoreFoundation 0x30be5477 __CFRunLoopDoSources0 + 204
  21  CoreFoundation 0x30be3c67 __CFRunLoopRun + 628
  22  CoreFoundation 0x30b4e729 CFRunLoopRunSpecific + 522
  23  CoreFoundation 0x30b4e50b CFRunLoopRunInMode + 104
  24  GraphicsServices 0x35abd6d3 GSEventRunModal + 136
  25  UIKit 0x334af871 UIApplicationMain + 1134
  26  feelgood 0x00341d47 main (main.m:16)
  27  libdyld.dylib 0x3b8b3ab7 start + 0
  </code></pre>