title: App crashing on runTransitionForCurrentState but no clue as to why
body: <p>I've tried searching for this, but no luck, so hoping there are some guru's who may know the answer.</p>
  
  <p>I'm seeing loads of reports in iTunes Connect of my app crashing with a particular stack trace, but the stack trace reveals nothing useful. </p>
  
  <pre><code>#0. Crashed: main
  0  UIKit                          0x1871100c0 __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 324
  1  UIKit                          0x1871100bc __56-[UIPresentationController runTransitionForCurrentState]_block_invoke + 320
  2  UIKit                          0x1870630c8 _runAfterCACommitDeferredBlocks + 292
  3  UIKit                          0x187070a80 _cleanUpAfterCAFlushAndRunDeferredBlocks + 92
  4  UIKit                          0x186da25a4 _afterCACommitHandler + 96
  5  CoreFoundation                 0x181c0c728 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
  6  CoreFoundation                 0x181c0a4cc __CFRunLoopDoObservers + 372
  7  CoreFoundation                 0x181c0a8fc __CFRunLoopRun + 928
  8  CoreFoundation                 0x181b34c50 CFRunLoopRunSpecific + 384
  9  GraphicsServices               0x18341c088 GSEventRunModal + 180
  10 UIKit                          0x186e1a088 UIApplicationMain + 204
  11 MyApp                          0x100082e6c main (main.m:19)
  12 libdyld.dylib                  0x1816d28b8 start + 4
  </code></pre>
  
  <p>No pattern to the reports, happens on iOS 9.1, 9.2, 9.3-10 and various iPhones and iPads and no clues to help reproduce it.</p>
  
  <p>Has anyone experienced something like this before and have some insight/suspicion on what may cause it?</p>