NullReferenceException error is thrown on changing Body, Aim and Noise property value in Virtual Camera preset asset.

Steps to repro:
1. Create a new Project.
2. Windows > Package Manager > Install Cinemachine package 2.3.4.
3. Cinemachine > Create Virtual Camera.
4. Create CinemachineVirtualCamera preset.
5. Select CinemachineVirtualCamera preset asset in the project view.

Actual Result:
NullReferenceException error is thrown in the console.

Expected Result:
No error in the console.

Reproducible in Package Version: 2.3.4, 2.3.3.

Tested in Unity Version:
2020.1.0a9, 2019.3.0b7, 2019.2.0f1.

Environment:
Windows 10 & Mac 10.14.

Stack trace:
NullReferenceException: Object reference not set to an instance of an object
Cinemachine.Editor.CinemachineVirtualCameraEditor.SetPipelineStage (Cinemachine.CinemachineCore+Stage stage, System.Type type) (at Library/PackageCache/com.unity.cinemachine@2.3.4/Editor/Editors/CinemachineVirtualCameraEditor.cs:241)
Cinemachine.Editor.CinemachineVirtualCameraEditor.DrawPipelineInInspector () (at Library/PackageCache/com.unity.cinemachine@2.3.4/Editor/Editors/CinemachineVirtualCameraEditor.cs:141)
Cinemachine.Editor.CinemachineVirtualCameraEditor.OnInspectorGUI () (at Library/PackageCache/com.unity.cinemachine@2.3.4/Editor/Editors/CinemachineVirtualCameraEditor.cs:105)
UnityEditor.Presets.PresetEditor.DrawInternalInspector () (at <2a08bc3d8f9c4796ba99475f6f6c6a6b>:0)
UnityEditor.Presets.PresetEditor.DrawPresetData () (at <2a08bc3d8f9c4796ba99475f6f6c6a6b>:0)
UnityEditor.Presets.PresetEditor.OnInspectorGUI () (at <2a08bc3d8f9c4796ba99475f6f6c6a6b>:0)
UnityEditor.UIElements.InspectorElement+<>c__DisplayClass54_0.<CreateIMGUIInspectorFromEditor>b__0 () (at <2a08bc3d8f9c4796ba99475f6f6c6a6b>:0)
UnityEditor.PopupCallbackInfo:SetEnumValueDelegate(Object, String[], Int32)