Steps to reproduce:

1. Download attached project and open in Unity

2. Observe the error in the Console:

NullReferenceException: Object reference not set to an instance of an object

UnityEditor.Rendering.RenderGraphViewer.UpdatePanelHeights () (at ./Library/PackageCache/com.unity.render-pipelines.core/Editor/RenderGraph/RenderGraphViewer.SidePanel.cs:390)

Actual results: No errors in the Console, if the RG Viewer was the active window before closing the Editor

Expected results:  NullReferenceException in the Console

Reproducible with versions: 

6000.0.0b12, 6000.0.0b16

Not reproducible with versions: 

2023.3.0b11
Tested on (OS): 

MacBook Pro (16-inch, 2021), CPU: Apple M1 Max, Memory: 64 GB, macOS: Ventura 13.3.1 (a) (22E772610a)