Don't check 'Custom Structure' Permalink radio option for the default permastruct. Fixes #18507

git-svn-id: https://develop.svn.wordpress.org/trunk@18590 602fd350-edb4-49c9-b593-d223f7449a82

wp-admin/options-permalink.php

@@ -164,6 +164,7 @@ if ( is_multisite() && !is_subdomain_install() && is_main_site() ) {
 }
 
 $structures = array(
+	0 => '',
 	1 => $prefix . '/%year%/%monthnum%/%day%/%postname%/',
 	2 => $prefix . '/%year%/%monthnum%/%postname%/',
 	3 => $prefix . '/' . _x( 'archives', 'sample permalink base' ) . '/%post_id%',