make sure that array key value is set and not empty

templates/default/compose_buttons.tpl

@@ -71,7 +71,7 @@ extract($t);
     }
    ?>
    <input type="submit" name="send" value="<?php echo _("Send"); ?>" />&nbsp;
-   <?php echo @$plugin_output['compose_button_row']; ?>
+   <?php if (!empty($plugin_output['compose_button_row'])) echo $plugin_output['compose_button_row']; ?>
   </td>
  </tr>
 </table>