Reproduction steps :
- Create a new HDRP template project
- Update HDRP Package to 7.1.6 (if in 7.1.5)
- Toggle OFF the scene effect settings
- Quit Unity
- Re-launch the same project
- Toggle ON the scene settings effect
- You should have the errors

The issue seems to arise ONLY when you quit the project with the toggle OFF
If the project is quit with the toggle ON, the issue is not here.

Also seems to happen only with HDRP version >= 7.1.6

For now, reproductible on :
- 2019.3.0f1 with HDRP 7.1.6
- 2019.3.0f2 with HDRP 7.1.6

- 2020.1.0a15 with HDRP/staging
- 2020.1.0a16 with HDRP/staging

- 2020.1.0a10 with HDRP 7.1.6
- 2020.1.0a12 with HDRP 7.1.6
- 2020.1.0a13 with HDRP 7.1.6
- 2020.1.0a14 with HDRP 7.1.6
- 2020.1.0a15 with HDRP 7.1.6
- 2020.1.0a16 with HDRP 7.1.6

NOT reproductible on :
2019.2.15f1 / HDRP 6.9.0
2019.2.15f1 / HDRP 6.9.1
2019.2.15f1 / HDRP 6.9.2

2018.4.14f1 / HDRP 4.1.0

Unity forum reference :
https://forum.unity.com/threads/2019-3-fog-is-broken.791649/
https://forum.unity.com/threads/hdrp-scene-is-not-visible-with-fog-in-preview-window.790259/
https://forum.unity.com/threads/hdrp-7-1-6-updatevolumetriclightingpercameradata-error.790013/

Text error below :

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.Rendering.HighDefinition.HDRenderPipeline.UpdateVolumetricLightingPerCameraData (UnityEngine.Rendering.HighDefinition.HDCamera hdCamera) (at C:/Users/remi.chapelain/Documents/GitHub/ScriptableRenderPipeline/com.unity.render-pipelines.high-definition/Runtime/Lighting/VolumetricLighting/VolumetricLighting.cs:342)
UnityEngine.Rendering.HighDefinition.HDCamera.Update (UnityEngine.Rendering.HighDefinition.FrameSettings currentFrameSettings, UnityEngine.Rendering.HighDefinition.HDRenderPipeline hdrp, UnityEngine.Rendering.MSAASamples msaaSamples, UnityEngine.Rendering.HighDefinition.XRPass xrPass) (at C:/Users/remi.chapelain/Documents/GitHub/ScriptableRenderPipeline/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/Camera/HDCamera.cs:355)
UnityEngine.Rendering.HighDefinition.HDRenderPipeline.TryCalculateFrameParameters (UnityEngine.Camera camera, UnityEngine.Rendering.HighDefinition.XRPass xrPass, UnityEngine.Rendering.HighDefinition.HDAdditionalCameraData& additionalCameraData, UnityEngine.Rendering.HighDefinition.HDCamera& hdCamera, UnityEngine.Rendering.ScriptableCullingParameters& cullingParams) (at C:/Users/remi.chapelain/Documents/GitHub/ScriptableRenderPipeline/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDRenderPipeline.cs:2551)
UnityEngine.Rendering.HighDefinition.HDRenderPipeline.Render (UnityEngine.Rendering.ScriptableRenderContext renderContext, UnityEngine.Camera[] cameras) (at C:/Users/remi.chapelain/Documents/GitHub/ScriptableRenderPipeline/com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDRenderPipeline.cs:1270)
UnityEngine.Rendering.RenderPipeline.InternalRender (UnityEngine.Rendering.ScriptableRenderContext context, UnityEngine.Camera[] cameras) (at <7c9de0535c4e4016a5abc17123191cf2>:0)
UnityEngine.Rendering.RenderPipelineManager.DoRenderLoop_Internal (UnityEngine.Rendering.RenderPipelineAsset pipe, UnityEngine.Camera[] cameras, System.IntPtr loopPtr, Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle safety) (at <7c9de0535c4e4016a5abc17123191cf2>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)