before this change:

* create a note, with text
  * `note` has a row with the text
	* `note_edit` doesn't have any matching row
* edit the note, removing all the text
  * the row in `note` has the new, empty, text
	* `note_edit` has a matching row, but its `oldText` is NULL

so the original text is lost

after this change, the row in `note_edit` always keeps the previous
text