On adding "Path Tracing" Override to "Volume Profile" asset throws NullReferenceException continuously when Scriptable Render Pipeline Settings is set to "None", refer the attached video.

Steps to repro:
1. Create a new project with HDRP Template
2. Upgrade High Definition RP Package to 7.1.5
3. Edit > Project Settings > Graphics > Scriptable Render Pipeline Settings > None
4. Assets > Create > Volume Profile
5. Select "New Volume Profile in the Project Window
6. Inspector > Add Override > Path Tracing

Actual Result:
NullReferenceException is thrown continuously on adding "Path Tracing" Override to "New Volume Profile" asset

Expected Result:
Path Tracing override should be attached to Volume Profile Assets without any exception being thrown

Reproducible on:
2020.1.0a14, 2019.3.0b12

Note: Unable to check on 7.1.2 because this package version was broken

Package Found version: 7.1.5
Package Working fine version: 7.1.1

Environment:
Windows 10 & macOS 10.14

Stack trace:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.Experimental.Rendering.HighDefinition.PathTracingEditor.OnInspectorGUI () (at Library/PackageCache/com.unity.render-pipelines.high-definition@7.1.5/Editor/RenderPipeline/PathTracing/PathTracingEditor.cs:41)
UnityEditor.Rendering.VolumeComponentEditor.OnInternalInspectorGUI () (at Library/PackageCache/com.unity.render-pipelines.core@7.1.5/Editor/Volume/VolumeComponentEditor.cs:225)
UnityEditor.Rendering.VolumeComponentListEditor.OnGUI () (at Library/PackageCache/com.unity.render-pipelines.core@7.1.5/Editor/Volume/VolumeComponentListEditor.cs:225)
UnityEditor.Rendering.VolumeProfileEditor.OnInspectorGUI () (at Library/PackageCache/com.unity.render-pipelines.core@7.1.5/Editor/Volume/VolumeProfileEditor.cs:25)
UnityEditor.UIElements.InspectorElement+<>c__DisplayClass55_0.<CreateIMGUIInspectorFromEditor>b__0 () (at <f77adbe680d5435ab56e2403863ec057>:0)
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)