Annotation view in VS fails to load

[cartermp]

1. Open a file that is tracked by git
2. Annotate (Blame)

[cartermp]

In this line, heir is null: https://github.com/Microsoft/visualfsharp/blob/master/vsintegration/src/FSharp.Editor/LanguageService/LanguageService.fs#L662

And we don't exhaustively check for null here.

[cartermp]

Not sure why it would start triggering in 15.7.

[cartermp]

Aha. It could still be null in the past, but #4328 captures it into a binding that it then attempts to . into. This was not observable in 15.6 because we didn't ship the miscfiles work until 15.7.