Invalid table headers after switching from both to column

[Marek Lewandowski]

1. Open any sample with CKEditor. (i.e. samples/replacebyclass.html)
2. Use following source.

` <table border="1" cellpadding="1" cellspacing="1" style="width:500px" summary="bar">

<caption>foo</caption> <thead>

<tr>

<th scope="col">aa</th> <th scope="col">aa</th> <th scope="col">aa</th>

</tr>

</thead> <tbody>

<tr>

<th scope="row">bb</th> <td>cc</td> <td>dd</td>

</tr> <tr>

<th scope="row">bb</th> <td>cc</td> <td>dd</td>

</tr>

</tbody>

</table> `

1. Right click at table, and use "Table Properties" menu item.
2. With "Headers" dropdown, set its value to "First Column".
3. Accept dialog by clicking OK.

Expected result:
First column should contain headers.

Current result:
There is no header (th element) in first row.

Additional info:

1. Tested with Chromium 42.0.2296.0.