lint: Fix syntax error regression

include/client/footer.inc.php

         </div>
     </div>
     <div id="footer">
-        <p>Copyright &copy; <?php echo date('Y'); ?> <?php echo $ost->company :? 'osTicket.com'; ?> - All rights reserved.</p>
+        <p>Copyright &copy; <?php echo date('Y'); ?> <?php echo $ost->company ?: 'osTicket.com'; ?> - All rights reserved.</p>
         <a id="poweredBy" href="http://osticket.com" target="_blank">Helpdesk software - powered by osTicket</a>
     </div>
 <div id="overlay"></div>