Steps to reproduce:

1. Install the 1.7.0 Asset Manager version
2. Open "Asset Manager" (Window -> Asset Manager) and check that data is displayed in the Asset Manager window
3. Go to the Package Manager window and select the "Asset Manager" package
4. In the "Version History" tab, select the older version
5. Please install it 
6. Open "Asset Manager" (Window -> Asset Manager) and check that data is displayed in the Asset Manager window
7. Go to the Package Manager window and select the "Asset Manager" package one more time
8. This time, select the latest version and update it again
9. Open the Asset Manager window and observe the result
10. If it is needed, repeat steps 3, 4, 5, and 6 several times with different Asset Manager versions and observe the result

Actual results: The Asset Manager window is empty. Console displays errors

Expected results: No errors in the Console window, and the Asset Manager window should always present data

Reproducible with versions: 1.7.0(6000.0.58f1, 6000.2.3f1, 6000.3.0b2)

Can’t test with versions: 

Tested on (OS): macOS - Sequoia 15.6.1

Notes: An error from the Console:

NullReferenceException: Object reference not set to an instance of an object
Unity.AssetManager.UI.Editor.PageManager.OnEnable () (at ./Library/PackageCache/com.unity.asset-manager-for-unity@a7a57dade898/Editor/UI/Services/PageManager.cs:134)
Unity.AssetManager.Core.Editor.BaseService.set_Enabled (System.Boolean value) (at ./Library/PackageCache/com.unity.asset-manager-for-unity@a7a57dade898/Editor/Core/Services/ServicesContainer.cs:32)
Unity.AssetManager.Core.Editor.ServicesContainer.EnableService (Unity.AssetManager.Core.Editor.IService service, System.Collections.Generic.Queue`1[T] serviceEnablingQueue) (at ./Library/PackageCache/com.unity.asset-manager-for-unity@a7a57dade898/Editor/Core/Services/ServicesContainer.cs:273)
Unity.AssetManager.Core.Editor.ServicesContainer.Resolve[T] () (at ./Library/PackageCache/com.unity.asset-manager-for-unity@a7a57dade898/Editor/Core/Services/ServicesContainer.cs:254)
Unity.AssetManager.UI.Editor.AssetManagerWindow.MenuEntry () (at ./Library/PackageCache/com.unity.asset-manager-for-unity@a7a57dade898/Editor/UI/UIElements/AssetManagerWindow.cs:27)