How to reproduce:

1. Create a URP 3D sample Project
2. Add an Adaptive Probe Volume to the Scene
3. Enable Adaptive Probe Volumes in the RP Asset (Light Probe System - Adaptive Probe Volumes)
4. Navigate to Window > Rendering > Lighting > Adaptive Probe Volumes
5. Generate Lighting
6. Close the Lighting Window and observe the Console

Actual result: Memory Leak Error is logged, when the Lighting Generation is close to finishing, Console is flooded by "NullReferenceException: Object reference not set to an instance of an object." Errors until the Background Task for Lighting Generation is cancelled.

Expected result: No issues when Generating Lighting and closing the Window as the Background tasks are still in process.

Reproducible with: 6000.0.2f1

Couldn't test with: 2021.3.38f1, 2022.3.28f1, 2023.1.20f1, 2023.20f1

Reproduced on: Windows 11, macOS Sonoma M1