browse/vault-ui: Ensure to leave the link column empty when a vault task failed

swh/web/templates/includes/vault-ui.html

@@ -144,6 +144,8 @@
           if (cooking_task.status == 'done') {
             dl_link = '<a class="btn btn-md btn-swh" href="' + cooking_task.fetch_url +
                       '"><i class="fa fa-download fa-fw" aria-hidden="true"></i>Download</a>';
+          } else if (cooking_task.status == 'failed') {
+            dl_link = '';
           }
           table_row += '<td class="vault-dl-link" style="width: 320px">' + dl_link + '</td>';
           table_row += '</tr>';