react-native-video（Cannot remove an observer for the key path "readyForDis...

描述：

切换播放源的时候报错：Exception thrown while executing UI block: Cannot remove an observer for the key path "readyForDisplay" from because it is not registered as an observer
解决：
在该框架的作者下面发现的
链接是这个：https://github.com/react-native-community/react-native-video/issues/907，有兴趣的可以去看看。
解决办法如下：
在xcode中找到RCTVideo.m文件，然后找到方法removePlayerLayer，将方法的实现修改为：

[_playerLayer removeFromSuperlayer];
    @try {
        [_playerLayer removeObserver:self forKeyPath:readyForDisplayKeyPath];
    } @catch (NSException *e) { }
      _playerLayer = nil;

用xcode重新编译运行即可解决。