Fixed bug with using just deleted empty note

This is a fix for a very annoying bug, triggered by starting selection after creating an empty note.
Here is a short summary:
 . create an empty note
 . start selecting some region inside a working basket
 . BasketScene::selectNotesIn() is called
 . ---> Note::selectIn() is called for each note
 . ------> Note::setSelected() is called
 . ---------> when 
 . ---------> if (!selected && basket()->editedNote() == this) {
 . --------->        basket()->closeEditor(); 
 . ---------> runs on that empty node it deletes it
 . ------> firstChild() method of the deleted note is called
. ---> note->next() of the deleted note is called