Undo / Redo Text Selection Bug

[J. Heard]

Steps to reproduce:

1. Type in a line of text
2. Press Enter
3. Type another line of text.
4. Select the second line of text.
5. Press the "backspace" key and delete all of the highlighted text, or just simply press backspace to delete all of the text.
6. Press Ctrl-Z or the Undo toolbar button

Observation: Only some of the deleted text is restored after pressing undo, and in some cases the entire second line of text is deleted. The behavior is sporadic, but reproducible. I've also noticed that if you have a lot of content in the editor, after calling the undo command the very last line of text will vanish.

Expected: The highlighted / deleted text should be restored as it was prior to deletion and the remainder of the content remains unchanged.

Notes: Redo performs in the same odd fashion. First noticed this behavior in the 2.6.3 version, but it's also reproducible in the nightly build:

​http://www.fckeditor.net/nightly/fckeditor/_samples/default.html