1.5.5 wp3.8 compat

git-svn-id: https://plugins.svn.wordpress.org/radio-buttons-for-taxonomies/trunk@823350 b8457f37-d9ea-0310-8a92-e5e31aec5664
1.5.6 php warning

git-svn-id: https://plugins.svn.wordpress.org/radio-buttons-for-taxonomies/trunk@823996 b8457f37-d9ea-0310-8a92-e5e31aec5664