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When i am playing video got this crash.Crashlytics log reportsCrashed: com.apple.main-thread0 libobjc.A.dylib 0x1845a67e8 object_isClass + 161 Foundation 0x185d103e8 KVO_IS_RETAINING_ALL_OBSERVERS_OF_THIS_OBJECT_IF_IT_CRASHES_AN_OBSERVER_WAS_OVERRELEASED_OR_SMASHED + 682 Foundation 0x185d0e8ec NSKeyValueWillChangeWithPerThreadPendingNotifications + 3003 AVFoundation 0x18abb60f8 -[AVPlayerItem willChangeValueForKey:] + 964 AVFoundation 0x18abc7ff0 -[AVPlayerItem _updatePropertyCacheAndTriggerKVOForPlayer:usingKeys:] + 2005 AVFoundation 0x18abb959c __60-[AVPlayerItem _informObserversAboutAvailabilityOfDuration:]_block_invoke_2 + 1846 libdispatch.dylib 0x184cdd088 _dispatch_call_block_and_release + 247 libdispatch.dylib 0x184cdd048 _dispatch_client_callout + 168 libdispatch.dylib 0x184d1ddfc _dispatch_main_queue_callback_4CF$VARIANT$armv81 + 9689 CoreFoundation 0x185301eb0 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 1210 CoreFoundation 0x1852ffa8c __CFRunLoopRun + 201211 CoreFoundation 0x18521ffb8 CFRunLoopRunSpecific + 43612 GraphicsServices 0x1870b7f84 GSEventRunModal + 10013 UIKit 0x18e7f42f4 UIApplicationMain + 20814 VZFiOSMobile 0x10475b340 main (main.m:17)15 libdyld.dylib 0x184d4256c start + 4Why does this happens and what I can do to avoid this?