"ArgumentException: Object at index 0 is null" exception is thrown on deleting the script from Visual Studio.

Steps to repro:
1. Open the attached project.
2. Assets Menu > Open C# Project.
3. In Visual Studio, delete Test1.cs script from the Solution Explorer window.
4. Focus back to Unity Editor.

Actual Result:
Script deleted with an exception in the Unity Console.

Expected Result:
The script deletes.

Reproducible with:
2019.3.0a7, 2019.3.0a2

Working Fine with:
2019.3.0a1, 2019.2.0b2.

Environment:
Only on Windows

Stack trace:
ArgumentException: Object at index 0 is null
UnityEditor.SerializedObject..ctor (UnityEngine.Object[] objs, UnityEngine.Object context) (at C:/buildslave/unity/build/Editor/Mono/SerializedObject.bindings.cs:39)
UnityEditor.Editor.GetSerializedObjectInternal () (at C:/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:553)
UnityEditor.Editor.get_serializedObject () (at C:/buildslave/unity/build/Editor/Mono/Inspector/Editor.cs:452)
UnityEditor.Experimental.AssetImporters.AssetImporterEditor.FixInspectorCache () (at C:/buildslave/unity/build/Modules/AssetPipelineEditor/ImportSettings/AssetImporterEditor.cs:203)
UnityEditor.AssemblyReloadEvents.OnAfterAssemblyReload () (at C:/buildslave/unity/build/Editor/Mono/AssemblyReloadEvents.cs:22)