Steps to reproduce:
1. Create new Unity project
2. Install Polybrush and Services Tooling packages via Package Manager
3. Right-click in Project window and navigate Create > Polybrush
4. Select and create “Prefab Palette” Asset
5. Right-click in Project window and navigate Create > Services
6. Select and create “Deployment Definition” Asset
7. Once “new_deployment_definition” Asset is created in Project window, delete it
8. Observe the Console window

Actual results: Error is thrown in the Console window “NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Polybrush.PostProcessPrefabs.OnPostprocessAllAssets (System.String[] importedAssets, System.String[] deletedAssets, System.String[] movedAssets, System.String[] movedFromAssetPaths) (at ./Library/PackageCache/com.unity.polybrush@a5500a61e57c/Editor/Utility/PostProcessPrefabs.cs:68)”
Expected results: No errors are thrown in the Console

Reproducible with versions: 1.2.1 (6000.0.62f1, 6000.2.11f1, 6000.3.0b9, 6000.4.0a4)

Tested on (OS): macOS SiliconbTahoe 26.0 (M1)