Bug with BR tag

Hi, help please.
To see the problem you need

1. Open http://ckeditor.com/demo#full
2. Switch to source-mode and paste:
<p>test1
<br />test2
<br />
<br />
</p>
<p>test2</p>

3. Then switch wysiwyg/source mode few times. You'll have something like this:

<p>test1<br />
test2<br />
&nbsp;</p>

<p>test2</p>

Second BR-tag has been replaced by &nbsp;

Thank you.