因为注册时机问题,在原生要再注册一次插件并且把根控制器传进去
flutterboost是去自动注册image_picker,那时候还没有根控制器,创建完根控制器自己再注册一遍,应该就没问题了
NSObject<FlutterPluginRegistrar>* registrar = [engine registrarForPlugin:@"plugins.flutter.io/image_picker"];
[FLTImagePickerPlugin registerWithRegistrar:registrar];