Index: categories_event_handler.php
===================================================================
--- categories_event_handler.php	(revision 14318)
+++ categories_event_handler.php	(working copy)
@@ -1591,7 +1591,8 @@
 
 			$root_category = $this->Application->getBaseCategory();
 
-			if (($object->GetDBField('ParentId') == $root_category) && ($object->GetDBField('Template') == CATEGORY_TEMPLATE_INHERIT)) {
+			if ( file_exists(FULL_PATH . '/themes') && ($object->GetDBField('ParentId') == $root_category) && ($object->GetDBField('Template') == CATEGORY_TEMPLATE_INHERIT) ) {
+				// there are themes + creating top level category
 				$object->SetError('Template', 'no_inherit');
 			}