Fix the "reset to default" button showing up for the color scheme field on brand new menu items. There's a small implementation difference between "use default color settings" (= null) and "no custom colors specified" (= false).

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@886818 b8457f37-d9ea-0310-8a92-e5e31aec5664