Issue #3256897: menu-icon class not re-applied correctly

Closes #3256897

simple_menu_icons.module

@@ -234,9 +234,10 @@ function _simple_menu_icons_preprocess_menu_item_recursive(&$item) {
     return;
   }
 
-  $mlid = $link_plugin['metadata']['entity_id'];
-  $item['attributes']->addClass('menu-icon');
-  $item['attributes']->addClass('menu-icon-' . $mlid);
+  if (!empty($link_plugin['options']['menu_icon']['fid'])) {
+    $mlid = $link_plugin['metadata']['entity_id'];
+    $item['attributes']->addClass('menu-icon menu-icon-' . $mlid);
+  }
 
   if (!empty($item['below'])) {
     foreach ($item['below'] as $key => &$value) {