Keep editor in sync with selected note in NoteList

[mirka]

Based on #1218

This is a fix for an inconsistency in the UI state, where the selected note in the Note List (highlighted in blue) could get out of sync with the note shown in the editor.

There were at least two cases where this would occur:

• Start searching for a note, and the editor will continue showing the initially selected note even when the query doesn't match it anymore.
• When you switch from All Notes to the Trash view, the first trashed note is selected blue in the Note List, but the editor is blank.

[roundhill]

• Start searching for a note, and the editor will continue showing the initially selected note even when the query doesn't match it anymore.

This always bugged me, yay!

[roundhill]

Looks good