-NullReferenceException error is thrown on installing any package when New scene Template window is open.
-Template window becomes blank.

Steps to repro:
1. Create a new project
2. Press "CTRL + N".
3. Windows > Package Manager > 2D SproteShape > Install.

Actual Result:
NullReferenceException error in the console.

Expected Result:
No errors in the console.

Reproducible in:
2020.2.0b1, 2020.2.0a15.

Note: Scene Template is available from 2020.2.0a15.

Environment:
Occurring on Windows 10 & Mac 10.15.

Stacktrace:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.SceneTemplate.SceneTemplateDialog.OnTemplateListViewSelectionChanged (System.Collections.Generic.IEnumerable`1[T] oldSelection, System.Collections.Generic.IEnumerable`1[T] newSelection) (at <a54f4468576a4ae592f9407f1bc66834>:0)
UnityEditor.SceneTemplate.GridView.SetSelection (System.Collections.Generic.IEnumerable`1[T] itemToSelect) (at <a54f4468576a4ae592f9407f1bc66834>:0)
UnityEditor.SceneTemplate.GridView.SetSelection (UnityEditor.SceneTemplate.GridView+Item itemToSelect) (at <a54f4468576a4ae592f9407f1bc66834>:0)
UnityEditor.SceneTemplate.SceneTemplateDialog.CreateAllSceneTemplateListsUI (UnityEngine.UIElements.VisualElement rootContainer) (at <a54f4468576a4ae592f9407f1bc66834>:0)
UnityEditor.SceneTemplate.SceneTemplateDialog.BuildUI () (at <a54f4468576a4ae592f9407f1bc66834>:0)
UnityEditor.SceneTemplate.SceneTemplateDialog.OnEnable () (at <a54f4468576a4ae592f9407f1bc66834>:0)