Mobile: Fixes #11384: Fix switching notes then unloading app causes blank screen

[personalizedrefrigerator]

Summary

This pull request updates Note.tsx to:

1. Continue displaying the previous note even if selectedNoteIds is empty.
2. Not disable the folder picker if selectedNoteIds is empty.

Fixes #11384.

Note

This pull request targets release-3.1.

Explanation

After following a link or changing the parent folder of the open note, state.selectedNoteIds can contain notes from different (unselected) folders. When refreshNotes is called, it removes notes from selectedNoteIds if they are not in the selected notebook/tag/smart filter. This causes selectedNoteIds to be set to [] when refreshNotes is called after moving the open note to a different folder or following a link to a note in a different folder.

Testing plan

Android 13:

1. Create two notes in different notebooks.
2. Add a link from one note to the other.
3. Open the note with the link from the notes list.
4. Follow the link.
5. Turn the device off.
6. Turn the device back on.
7. Verify that the note is still open.
8. Verify that the "select folder" dropdown is not disabled.
9. Change the note's parent folder using the "select folder" dropdown.
10. Press the back button.
11. Verify that the note from step 3 is open.
12. Press the back button.
13. Verify that both notes are visible in the notes list.
14. Select both notes.
15. Using the "move to notebook..." dropdown, move both notes to a different notebook.