Browser back button doesn't close editor #4277
Description
If you're editing a document, and click the browser's back button, the expectation is that the editing session is closed, and you return to the file list.
However, instead either nothing happens (Chrome), or the editor iframe becomes white (Firefox).
Observed in Nextcloud 29.0.8 and 30.0.2, with latest compatible richdocuments apps.
Based on my memory, it seems to be a regression compared to some older Nextcloud version.