fixed admin menu serialization issue

git-svn-id: https://plugins.svn.wordpress.org/ag-custom-admin/trunk@904358 b8457f37-d9ea-0310-8a92-e5e31aec5664
v 1.3.6

git-svn-id: https://plugins.svn.wordpress.org/ag-custom-admin/trunk@904359 b8457f37-d9ea-0310-8a92-e5e31aec5664