Bug 38753: Missing table cells breaks OPAC charges table

This patch adds a couple of instances of the empty cell required by
DataTables to enable responsive behavior. The mismatch between table
headers and table cells causes DataTables to fail.

To test you must log in to the OPAC as a user with charges and credit.

- Apply the patch and go to Patrons in the staff interface.
- Find and view a patron record. Click "Accounting" in the sidebar menu.
- Use the "Create manual invoice" and "Create manual credit" tabs to
  create at least one charge and a credit which is greater than the
  charges.
- Log in to the OPAC as that user and go to their Charges tab.
- The charges table shoud look correct, with DataTables sorting
  indicators on the table headers to indicate that DataTables is
  working.

Sponsored-by: Athens County Public Libraries
Signed-off-by: Roman Dolny <roman.dolny@jezuici.pl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit b49cac544f)
Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>

koha-tmpl/opac-tmpl/bootstrap/en/includes/account-table.inc

@@ -74,11 +74,13 @@
                         </td>
                         <td class="credit">[% outstanding_credit.amount * -1 | $Price %]</td>
                         <td class="credit">[% outstanding_credit.amountoutstanding * -1 | $Price %]</td>
+                        <td></td>
                     </tr>
                 [% END %]
                 <tr>
                     <th class="sum" colspan="[% COLSPAN | html %]">Total due if credit(s) applied:</th>
                     <td class="sum">[% total + outstanding_credits.total_outstanding | $Price %]</td>
+                    <td></td>
                 </tr>
                 [% END %]
             </tfoot>