Fix clicking on the "Last Ping" cell.

templates/front/my_checks_desktop.html

@@ -77,7 +77,7 @@
                 </span>
             </span>
         </td>
-        <td id="lpd-{{ check.code}}">
+        <td id="lpd-{{ check.code}}" class="last-ping-cell">
             {% include "front/last_ping_cell.html" with check=check %}
         </td>
         <td>