If you delete the Mobile Notifications Settings asset while viewing it via the Project Settings Window, several NullReferenceExceptions will occur in the console.

1. Open Unity
2. Open the attached project
3. Go to Edit > Project Settings > Mobile Notification Settings
4. Leaving the Project Settings Window open, find Assets/Editor/com.unity.mobile.notifications/NotificationSettings.asset in the Project View
5. Delete the asset

Expected Result:
No errors or exceptions appear in the console when the asset is deleted.

Actual Result:
Two NullReferenceExceptions occur in the console:

NullReferenceException: Object reference not set to an instance of an object
UnityEditor.EditorGUIUtility.DrawEditorHeaderItems (UnityEngine.Rect rectangle, UnityEngine.Object[] targetObjs, System.Single spacing) (at <5e3c867fd4cc418f8c0584e878722a23>:0)

NullReferenceException: Object reference not set to an instance of an object
UnityEngine.UIElements.UIR.RenderChain.Render (UnityEngine.Rect topRect, UnityEngine.Matrix4x4 projection) (at <77aeb935848248f4a7c51786da67afda>:0)

Tested on Windows.

Occurs on package version 1.0.2 using 2019.3.0a10