Steps to reproduce:

1. Open any Project
2. Open the Package Manager (Window > Package Management > Package Manager)
3. Click the "+" button in the top left corner of the Window can select "Create Package", enter any name and create a Package
4. When the Package is created and selected, click the "Manage" dropdown button and select "Edit Manifest"
5. In the Inspector click the kebab menu icon in the top right corner of the Inspector Window and select "Properties..."
6. In the newly opened Focused Inspector switch the Importer type from Manifest to Text
7. Then switch back to Text and observe the Console

Actual results: Error "The previous instance of UnityEditor.PackageManager.UI.Internal.PackageManifestImporterEditor has not been disposed correctly. Make sure you are calling base.OnDisable() in your AssetImporterEditor implementation.
UnityEditor.EditorGUI/PopupCallbackInfo:SetEnumValueDelegate (object,string[],int)" is logged

Expected results: No Error is logged and Importer type is switched without issues

Reproducible with versions: 6000.0.65f1, 6000.2.15f1, 6000.3.4f1, 6000.4.0b4, 6000.5.0a4

Tested on (OS): Windows 11