Invalid table colspans break row insert

[Matthew Leffler]

Reproduce steps:

1. Open demo
2. Paste the following in source:

   <table>
   	<tbody>
   		<tr>
   			<td colspan="4">
   				First row</td>
   		</tr>
   		<tr>
   			<td>
   				1</td>
   			<td colspan="2">
   				2</td>
   		</tr>
   	</tbody>
   </table>
   

3. Click source again to leave source mode.
4. Right click table and insert row before or after.

Expected result

The row will be inserted before or after, respectively.

Actual result

No row is inserted and in webkit browsers a JS error is thrown:

Uncaught TypeError: Cannot read property 'rowSpan' of undefined

Browsers

This was tested with Chrome 12, FF5, and Safari 5.1.

[Jakub Ś]

This is a duplicate of #7996