XWIKI-21778: Admin section: make the Extension section pass webstanda…

…rd tests

* Fixed webs standard tests, successfully ran with the searchSuggest page too:
mvn clean install -f xwiki-platform-distribution/xwiki-platform-distribution-flavor/xwiki-platform-distribution-flavor-test/xwiki-platform-distribution-flavor-test-webstandards -Dxwiki.test.startXWiki=false

xwiki-platform-core/xwiki-platform-search/xwiki-platform-search-ui/src/main/resources/XWiki/SearchSuggestSourceSheet.xml

@@ -75,7 +75,7 @@
         $services.rendering.escape($!object.getProperty($property.name).value, 'xwiki/2.1')
       #end
   #else
-    :
+    : (% class='hidden' %)
   #end
 #end
 )))