not empty table cells are removed

[belda]

The editor removes certain cells, which causes the remaining cells to shift, thus violating the contents.

Removed are not only empty cells (which is caused by removing empty tags), but also cells with   and cells with 0 character.

It happens with the stable version and with the 0.5 beta 1 versoin also, others were not tested.

exemple of data, that gets corrupted

<table  class="zajezd skipasy">
<tr class="row0">
   <th rowspan="2">Plošná platnost</th>
   <th rowspan="2">Délka platnosti</th>
   <th rowspan="2">Věková kategorie</th>
   <th>06.12.</th>
   <th>10.01.</th>
   <th>31.01.</th>
   <th>07.02.</th>
</tr>
<tr class="row1">
   <th>20.12.</th>
   <th>31.01.</th>
   <th>07.02.</th>
   <th>07.03.</th>
</tr>
<tr class="row0">
   <th  rowspan="4">4 Valli</th>
   <th  rowspan="2">4 dny</th>
   <th >dospělý</th>
   <td colspan="4">zahrnut v základní ceně</td>
</tr>
<tr class="row1">
   <th >junior / senior</th>
   <td>0</td>
   <td>-900</td>
   <td>-950</td>
   <td>-1,150</td>
</tr>
<tr class="row0">
   <th  rowspan="2">5 dní</th>
   <th >dospělý</th>
   <td>100</td>
   <td>200</td>
   <td>300</td>
   <td>300</td>
</tr>
<tr class="row1">
   <th >junior / senior</th>
   <td>100</td>
   <td>-750</td>
   <td>-750</td>
   <td>-900</td>
</tr>
<tr class="row0">
   <th  rowspan="4">Alta
Valtellina</th>
   <th  rowspan="2">4 dny</th>
   <th >dospělý</th>
   <td>1,200</td>
   <td>1,450</td>
   <td>1,100</td>
   <td>1,350</td>
</tr>
<tr class="row1">
   <th >junior / senior</th>
   <td>300</td>
   <td>150</td>
   <td>-200</td>
   <td>-200</td>
</tr>
<tr class="row0">
   <th  rowspan="2">5 dní</th>
   <th >dospělý</th>
   <td>1,400</td>
   <td>1,800</td>
   <td>1,450</td>
   <td>1,750</td>
</tr>
<tr class="row1">
   <th >junior / senior</th>
   <td>450</td>
   <td>350</td>
   <td>0</td>
   <td>50</td>
</tr>
<tr class="row0">
   <th  colspan="3">nelyžaři a kategorie bimbo</th>
   <td>-1,700</td>
   <td>-2,900</td>
   <td>-3,250</td>
   <td>-3,850</td>
</tr>
<tr class="row1">
   <th rowspan="2">Plošná platnost</th>
   <th rowspan="2">Délka platnosti</th>
   <th rowspan="2">Věková kategorie</th>
   <th>07.03.</th>
   <th>14.03.</th>
   <th>21.03.</th>
   <th>28.03.</th>
</tr>
<tr class="row0">
   <th>14.03.</th>
   <th>21.03.</th>
   <th>28.03.</th>
   <th>18.04.</th>
</tr>
<tr class="row1">
   <th  rowspan="4">4 Valli</th>
   <th  rowspan="2">4 dny</th>
   <th >dospělý</th>
   <td colspan="4">zahrnut v základní ceně</td>
</tr>
<tr class="row0">
   <th >junior / senior</th>
   <td>-950</td>
   <td>-900</td>
   <td>-900</td>
   <td>-700</td>
</tr>
<tr class="row1">
   <th  rowspan="2">5 dní</th>
   <th >dospělý</th>
   <td>300</td>
   <td>200</td>
   <td>200</td>
   <td>150</td>
</tr>
<tr class="row0">
   <th >junior / senior</th>
   <td>-750</td>
   <td>-750</td>
   <td>-750</td>
   <td>-550</td>
</tr>
<tr class="row1">
   <th  rowspan="4">Alta
Valtellina</th>
   <th  rowspan="2">4 dny</th>
   <th >dospělý</th>
   <td>1,950</td>
   <td>2,300</td>
   <td>1,450</td>
   <td>2,150</td>
</tr>
<tr class="row0">
   <th >junior / senior</th>
   <td>400</td>
   <td>750</td>
   <td>150</td>
   <td>850</td>
</tr>
<tr class="row1">
   <th  rowspan="2">5 dní</th>
   <th >dospělý</th>
   <td>2,350</td>
   <td>2,700</td>
   <td>1,800</td>
   <td>2,500</td>
</tr>
<tr class="row0">
   <th >junior / senior</th>
   <td>650</td>
   <td>1,000</td>
   <td>350</td>
   <td>1,050</td>
</tr>
<tr class="row1">
   <th  colspan="3">nelyžaři a kategorie bimbo</th>
   <td>-3,250</td>
   <td>-2,900</td>
   <td>-2,900</td>
   <td>-2,200</td>
</tr>
</table>

[jf.hovinne]

Should be fixed by r558 (simply remove '|td' from the regex).

Related to #107 and #134.