title: Crashes with AdMob and Xamarin
body: <p>We have over 20K crashes with the same error from the Xamarin AdMob bindings. Since they all mention MP4 I am wondering if it could be related to video ads but we only use AdMob for banner ads in our app. </p>
  
  <p>Anyone have any tips to what can cause this? Since we can have 5000 crashes in a single day I feel it can't be "only" memory issues.  </p>
  
  <pre><code>Fatal Exception: NSInvalidArgumentException
  -[FNFLocalMp4Asset _absoluteURL]: unrecognized selector sent to instance 0x110df8ac0
  
  Fatal Exception: NSInvalidArgumentException
  0  CoreFoundation                 0x1939501c0 __exceptionPreprocess
  1  libobjc.A.dylib                0x19238855c objc_exception_throw
  2  CoreFoundation                 0x193957278 __methodDescriptionForSelector
  3  CoreFoundation                 0x193954278 ___forwarding___
  4  CoreFoundation                 0x19384e59c _CF_forwarding_prep_0
  5  AVFoundation                   0x19aff57cc -[AVPlayerItem initWithAsset:automaticallyLoadedAssetKeys:]
  6  NDC2010                        0x100199c74 GADAdSizeFromNSValue
  7  NDC2010                        0x1001c6eec GADAdSizeFromNSValue
  8  libdispatch.dylib              0x1927d9200 _dispatch_call_block_and_release
  9  libdispatch.dylib              0x1927d91c0 _dispatch_client_callout
  10 libdispatch.dylib              0x1927ddd6c _dispatch_main_queue_callback_4CF
  11 CoreFoundation                 0x1938fdf2c __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
  12 CoreFoundation                 0x1938fbb18 __CFRunLoopRun
  13 CoreFoundation                 0x19382a048 CFRunLoopRunSpecific
  14 GraphicsServices               0x1952ad198 GSEventRunModal
  15 UIKit                          0x199804628 (Missing)
  16 UIKit                          0x1997ff360 (Missing)
  17 NDC2010                        0x100861614 WriteZStream
  18 NDC2010                        0x1007cf7dc WriteZStream
  19 NDC2010                        0x1003faee4 WriteZStream
  20 NDC2010                        0x100764664 WriteZStream
  21 Mono                           0x101469c08 (Missing)
  22 Mono                           0x1014daa6c (Missing)
  23 Mono                           0x1014dd050 (Missing)
  24 Mono                           0x1014dcc6c (Missing)
  25 Mono                           0x10144e224 (Missing)
  26 NDC2010                        0x1003f3f8c xamarin_GetFolderPath
  27 NDC2010                        0x100efa800 WriteZStream
  28 libdispatch.dylib              0x19280c5b8 (Missing)
  </code></pre>