title: ios fatal exception error - NSInvalidArgumentException NSInvalidArgumentException
body: <p>I got crash issue from Crashlytics. </p>
  
  <p>UIKit
  -[UIView(Internal) _addSubview:positioned:relativeTo:]</p>
  
  <p>Fatal Exception: NSInvalidArgumentException NSInvalidArgumentException
  Can't add self as subview</p>
  
  <pre><code>Thread : Fatal Exception: NSInvalidArgumentException
  0  CoreFoundation                 0x2e9a0f4b __exceptionPreprocess + 130
  1  libobjc.A.dylib                0x391376af objc_exception_throw + 38
  2  CoreFoundation                 0x2e9a0e8d -[NSException initWithCoder:]
  3  UIKit                          0x3111f48f -[UIView(Internal) _addSubview:positioned:relativeTo:] + 110
  4  UIKit                          0x3111f417 -[UIView(Hierarchy) addSubview:] + 30
  5  UIKit                          0x312e7c2f __53-[_UINavigationParallaxTransition animateTransition:]_block_invoke + 1402
  6  UIKit                          0x311256e5 +[UIView(Animation) performWithoutAnimation:] + 72
  7  UIKit                          0x312e7479 -[_UINavigationParallaxTransition animateTransition:] + 728
  8  UIKit                          0x312a4ba7 -[UINavigationController _startCustomTransition:] + 2614
  9  UIKit                          0x311c2273 -[UINavigationController _startDeferredTransitionIfNeeded:] + 418
  10 UIKit                          0x311c207d -[UINavigationController __viewWillLayoutSubviews] + 44
  11 UIKit                          0x311c2015 -[UILayoutContainerView layoutSubviews] + 184
  12 UIKit                          0x31113da3 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 346
  13 QuartzCore                     0x30d9ac6b -[CALayer layoutSublayers] + 142
  14 QuartzCore                     0x30d9647b CA::Layer::layout_if_needed(CA::Transaction*) + 350
  15 QuartzCore                     0x30d9630d CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 16
  16 QuartzCore                     0x30d95d1f CA::Context::commit_transaction(CA::Transaction*) + 230
  17 QuartzCore                     0x30d95b2f CA::Transaction::commit() + 314
  18 QuartzCore                     0x30d8f85d CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 56
  19 CoreFoundation                 0x2e96c1cd 
  20 CoreFoundation                 0x2e969b71 __CFRunLoopDoObservers + 284
  21 CoreFoundation                 0x2e969eb3 __CFRunLoopRun + 730
  22 CoreFoundation                 0x2e8d4c27 CFRunLoopRunSpecific + 522
  23 CoreFoundation                 0x2e8d4a0b CFRunLoopRunInMode + 106
  24 GraphicsServices               0x335c8283 GSEventRunModal + 138
  25 UIKit                          0x31178049 UIApplicationMain + 1136
  26 Tapastic                       0x000764ef main (main.m:16)
  27 Tapastic                       0x00075bf0 start
  </code></pre>
  
  <p>I cannot find where this crash happened in codes. So how can I find where this crash is and fix it? Please let me know. Thanks in advance. </p>