[IE] Outdent break list numbering

[garry.yao]

This is derived from #1491.

Reproducing Procedures

1. Open the 'replace by class' sample page.
2. Load the document with following content:

    <ol>
   	<li>
   		item1
   		<ol>
   			<li>
   				&nbsp;^</li>
   		</ol>
   	</li>
   	<li>
   		item2</li>
   </ol>
   

3. Click 'outdent' button;
   • Actual Result: The list numbering is incorrect as: 1,1,2;
   • Expected Result: The list numbering is: 1,2,3;

[garry.yao]

Fixed by recent changes in trunk.