[video_player]: Fix texture unregistration callback signature

Flutter's video plugin can cause crashes after a closing a flutter view on simulator model iPhone X or higher

Co-authored-by: Mike Diarmid <mike.diarmid@gmail.com>

Author: shihchanghsiungsonos

packages/video_player/video_player/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 2.0.0-nullsafety.9
+
+* Fixed an issue where a crash can occur after a closing a video player view on iOS.
+
 ## 2.0.0-nullsafety.8
 
 * Migrated from deprecated `defaultBinaryMessenger`.

packages/video_player/video_player/ios/Classes/FLTVideoPlayerPlugin.m

@@ -392,7 +392,7 @@ - (CVPixelBufferRef)copyPixelBuffer {
   }
 }
 
-- (void)onTextureUnregistered {
+- (void)onTextureUnregistered:(NSObject<FlutterTexture>*)texture {
   dispatch_async(dispatch_get_main_queue(), ^{
     [self dispose];
   });

packages/video_player/video_player/pubspec.yaml

@@ -4,7 +4,7 @@ description: Flutter plugin for displaying inline video with other Flutter
 # 0.10.y+z is compatible with 1.0.0, if you land a breaking change bump
 # the version to 2.0.0.
 # See more details: https://github.com/flutter/flutter/wiki/Package-migration-to-1.0.0
-version: 2.0.0-nullsafety.8
+version: 2.0.0-nullsafety.9
 homepage: https://github.com/flutter/plugins/tree/master/packages/video_player/video_player
 
 flutter: