fix html validator error

iframe.html

@@ -753,13 +753,13 @@
   <!-- Content Wrapper. Contains page content -->
   <div class="content-wrapper iframe-mode" data-widget="iframe" data-loading-screen="750">
     <div class="nav navbar navbar-expand-lg navbar-white navbar-light border-bottom p-0">
-      <li class="nav-item dropdown">
+      <div class="nav-item dropdown">
         <a class="nav-link bg-danger dropdown-toggle" data-toggle="dropdown" href="#" role="button" aria-haspopup="true" aria-expanded="false">Close</a>
         <div class="dropdown-menu mt-0">
           <a class="dropdown-item" href="#" data-widget="iframe-close" data-type="all">Close All</a>
           <a class="dropdown-item" href="#" data-widget="iframe-close" data-type="all-other">Close All Other</a>
         </div>
-      </li>
+      </div>
       <a class="nav-link bg-light" href="#" data-widget="iframe-scrollleft"><i class="fas fa-angle-double-left"></i></a>
       <ul class="navbar-nav" role="tablist"></ul>
       <a class="nav-link bg-light" href="#" data-widget="iframe-scrollright"><i class="fas fa-angle-double-right"></i></a>