DirectoryNotFoundException: Could not find a part of the path '...\unityLibrary'

[AuMaHub]

Describe the bug
When I do Flutter -> Export Android in Unity, an error occurs.

DirectoryNotFoundException: Could not find a part of the path 'C:\VSCRepost\Flutter\likers-eng\unity\SlapChamp\Builds\SLAP CHAMP.apk\unityLibrary'.
System.IO.__Error.WinIOError (System.Int32 errorCode, System.String maybeFullPath) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.FileSystemEnumerableIterator`1[TSource].HandleError (System.Int32 hr, System.String path) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.FileSystemEnumerableIterator`1[TSource].CommonInit () (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.FileSystemEnumerableIterator`1[TSource]..ctor (System.String path, System.String originalUserPath, System.String searchPattern, System.IO.SearchOption searchOption, System.IO.SearchResultHandler`1[TSource] resultHandler, System.Boolean checkHost) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.FileSystemEnumerableFactory.CreateFileNameIterator (System.String path, System.String originalUserPath, System.String searchPattern, System.Boolean includeFiles, System.Boolean includeDirs, System.IO.SearchOption searchOption, System.Boolean checkHost) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.Directory.InternalGetFileDirectoryNames (System.String path, System.String userPathOriginal, System.String searchPattern, System.Boolean includeFiles, System.Boolean includeDirs, System.IO.SearchOption searchOption, System.Boolean checkHost) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.Directory.InternalGetDirectories (System.String path, System.String searchPattern, System.IO.SearchOption searchOption) (at <567df3e0919241ba98db88bec4c6696f>:0)
System.IO.Directory.GetDirectories (System.String path, System.String searchPattern, System.IO.SearchOption searchOption) (at <567df3e0919241ba98db88bec4c6696f>:0)
Build.Copy (System.String source, System.String destinationPath) (at Assets/FlutterUnityIntegration/Editor/Build.cs:134)
Build.DoBuildAndroid (System.String buildPath, System.Boolean isPlugin) (at Assets/FlutterUnityIntegration/Editor/Build.cs:59)
Build.DoBuildAndroidLibrary () (at Assets/FlutterUnityIntegration/Editor/Build.cs:23)

To Reproduce
Steps to reproduce the behavior:

1. Create unity folder in flutter project
2. Insert the Unity project into the unity folder
3. Change the Unity project to android (option follow the video.)
4. Click Export Android in the Flutter menu
5. Error content such as Describe the bug

Expected behavior
Normal android export worked fine.
I used FlutterUnityIntegration-v4.unitypackage, but expected it doesn't fit the 2019 version of Unity.

Screenshots
File structure

Unity (please complete the following information):

• OS: Android
• Version 28

Smartphone (please complete the following information):

• Device: Nexus 6
• OS: Android 10
• Version API 30

Additional context
Add any other context about the problem here.

[AuMaHub]

I tried raising the version of Unity and referring to #234 (comment) and succeeded.