Fix StatusBar crashing due to missing `doc` prop

[philippamarkovics]

Currently, StatusBar throws a type error during initial render because the doc prop is not being passed along to LensController. As remedy, we grab the doc from documentSession and pass it along for both the reader and the writer.

[michael]

We changed the API of LensWriter/Reader to take a DocumentSession instead of a Document so we can control realtime stuff outside of the editor. Very possible we introduced some regressions here. I will have look...