Play video MediaPlayback in Ipad is not showing video, only audio can be heard

#493 System info

Issue occurs on: iOS
Plugin version: ^0.3.11
Flutter doctor output:

```
[✓] Flutter (Channel stable, v1.17.5, on Mac OS X 10.15.6 19G73, locale en-ID)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
[!] Android Studio (version 4.0)
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
[✓] VS Code (version 1.47.1)
[✓] Connected device (2 available)

! Doctor found issues in 1 category.
```

## Steps to Reproduce

When I try with url https://bcovlive-a.akamaihd.net/4feb3ffbde6146549f02fc9d3822a3cb/ap-southeast-1/6107106512001/playlist.m3u8
the video is not appear, just audio can be heard

1.

## Logs

```
Runner[52659:507420] [assertion] Error acquiring assertion: {
userInfo = {
RBSAssertionAttribute = ;
}
}
```

flutter analyze no issue:
```
No issues found!
```

Here flutter doctor -v
```
[✓] Flutter (Channel stable, v1.17.5, on Mac OS X 10.15.6 19G73, locale en-ID)
• Flutter version 1.17.5 at /Users/ilhamamirullah/flutter
• Framework revision 8af6b2f038 (3 weeks ago), 2020-06-30 12:53:55 -0700
• Engine revision ee76268252
• Dart version 2.8.4

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
• Android SDK at /Users/ilhamamirullah/Library/Android/sdk
• Platform android-30, build-tools 30.0.0
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.6, Build version 11E708
• CocoaPods version 1.9.3

[!] Android Studio (version 4.0)
• Android Studio at /Applications/Android Studio.app/Contents
✗ Flutter plugin not installed; this adds Flutter specific functionality.
✗ Dart plugin not installed; this adds Dart specific functionality.
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)

[✓] VS Code (version 1.47.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.12.2

[✓] Connected device (2 available)
• iPhone SE (2nd generation) • ED05FA2D-572E-43E0-BF4B-0251F93EC18B • ios • com.apple.CoreSimulator.SimRuntime.iOS-13-6
(simulator)
• iPad Pro (12.9-inch) (4th generation) • 35401DB7-8968-4163-BA66-983BB5FCCA3F • ios • com.apple.CoreSimulator.SimRuntime.iOS-13-6
(simulator)

! Doctor found issues in 1 category.
```

Tái hiện báo cáo trong môi trường iPad/iOS 13.6 được liệt kê bằng HLS URL được cung cấp và phiên bản plugin ^0.3.11. Bắt đầu bằng cách lần theo điểm vào WebView iOS/phát media của plugin; được xem là hoàn tất khi video được render trong khi âm thanh vẫn nghe được, và log MediaPlayback được báo cáo đã được hiểu hoặc giải quyết.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.