Hooks - `useFragment` (sometimes) returns null when record is deleted

Version: `react-relay@11.0.2`

Issue: the return value for `useFragment` is null in some circumstances. The types suggest that this should not occur.

Repro in the example TODO app:
https://codesandbox.io/s/usefragment-returns-null-6tynl?file=/src/Todo.tsx:1027-1035

https://user-images.githubusercontent.com/489896/121592515-c8106980-ca08-11eb-89fb-ecff932b9fe9.mp4

Notes:
* A newly-created record can be deleted just fine. It is properly un-rendered.
* A record that existed at page load does not seem to be immediately removed from the connection, and it renders once more with `useFragment` returning `null`.

Using `@deleteEdge` (or the corresponding `updater` code, as is in the example TODO app) works fine. However, in our use case, the record also needs to be deleted in order to update other bits of UI.

Other approaches tried:
* using both `@deleteRecord` and `@deleteEdge` together (not yet supported?)
* in `updater` function, performing explicit deleteEdge and deleting the record in different orders (same result)

Thanks for reading!