title: iOS - NSISEngine crash
body: <p>Any idea what causes this crash or how to resolve this ? </p>
  
  <pre><code>Thread 11 Crashed:
  0   Foundation                           0x000000021c5b6368 ___chooseOutgoingRowHeadForIncomingRowHead_block_invoke + 24
  1   Foundation                           0x000000021c479130 __NSIndexSetEnumerate + 752
  2   Foundation                           0x000000021c5b37b0 _chooseOutgoingRowHeadForIncomingRowHead + 324
  3   Foundation                           0x000000021c5aec7c _minimizeConstantInObjectiveRow + 204
  4   Foundation                           0x000000021c3c45f4 -[NSISEngine _optimizeWithoutRebuilding] + 232
  5   Foundation                           0x000000021c3c4464 -[NSISEngine optimize] + 116
  6   Foundation                           0x000000021c3c4228 -[NSISEngine performPendingChangeNotifications] + 108
  7   UIKitCore                            0x000000024840c128 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2012
  8   QuartzCore                           0x000000021fece1f0 -[CALayer layoutSublayers] + 180
  9   UIKitCore                            0x0000000248381fa0 -[_UILabelLayer layoutSublayers] + 56
  10  QuartzCore                           0x000000021fed3198 CA::Layer::layout_if_needed(CA::Transaction*) + 328
  11  QuartzCore                           0x000000021fe360a8 CA::Context::commit_transaction(CA::Transaction*) + 344
  12  QuartzCore                           0x000000021fe64108 CA::Transaction::commit() + 636
  13  QuartzCore                           0x000000021fe65288 CA::Transaction::release_thread(void*) + 224
  14  libsystem_pthread.dylib              0x000000021b6634b4 _pthread_tsd_cleanup + 576
  15  libsystem_pthread.dylib              0x000000021b660904 _pthread_exit + 76
  16  libsystem_pthread.dylib              0x000000021b661508 _pthread_wqthread_exit + 92
  17  libsystem_pthread.dylib              0x000000021b66114c _pthread_wqthread + 356
  18  libsystem_pthread.dylib              0x000000021b663cd4 start_wqthread + 0
  </code></pre>