>>137

場所 Xamarin.VisualStudio.Inspector.XamarinInspectorPackage.RefreshInspectorSession() 場所 C:\d\lanes\4699\c8715752\source\xamarinvs\src\Features\VisualStudio.Inspector\Vsix\XamarinInspectorPackage.cs:行 136

でググった結果
↓

https://developercommunity.visualstudio.com/content/problem/55002/xamarin-nullreferenceexception-1.html