[IE7] Selection error when typing text after table

[Garry Yao]

The bug is only reproducible in and below IE7:

1. Use enterMode BR;
2. Load a table as initial contents:

   <table>
   	<tbody>
   	<tr>
   		<td>
   			text
   		</td>
   	</tr>
   	</tbody>
   </table>
   

3. Put the cursor after the table and start typing

• Actual Result: JavaScript error thrown;

[Garry Yao]

Regression of [6337].

[Garry Yao]

It looks like an IE bug when measuring the selection range, confirm it only happens with newly inserted text nodes after a table element at the end of document.

The patch fix the error when doesn't guarantee the correctness of range measurement in this case, while considering it's quite a edge case, we could work later to check a complete solution.