Fix possible crash if no content for login banner

include/staff/login.tpl.php

@@ -5,7 +5,7 @@ $info = ($_POST && $errors)?Format::htmlchars($_POST):array();
 <div id="loginBox">
     <h1 id="logo"><a href="index.php">osTicket Staff Control Panel</a></h1>
     <h3><?php echo Format::htmlchars($msg); ?></h3>
-    <div><?php echo Format::viewableImages($content->getBody()); ?></div>
+    <div><small><?php echo ($content) ? Format::viewableImages($content->getBody()) : ''; ?></small></div>
     <form action="login.php" method="post">
         <?php csrf_token(); ?>
         <input type="hidden" name="do" value="scplogin">