In section list, back button should take user back to Notebook list rather than close app
When you open a notebook from the notebook list, you are presented with a section list. Pressing the system back button on this view closes the app, rather than the expected behaviour of taking you back to the list of notebooks.
E.g. If I accidentally tap to open the wrong notebook, my automatic reaction is to press back, which closes the app and is highly frustrating. I then have to re-open the app and remember to tap the notebook name in top left to get back to the notebook list.
This behaviour is contrary to the notes list within a section, where if the back button is pressed the user is taken back to the section list.