fix php notice error

git-svn-id: https://plugins.svn.wordpress.org/oh-youtube-in-lightbox/trunk@843593 b8457f37-d9ea-0310-8a92-e5e31aec5664
fix php notice error

git-svn-id: https://plugins.svn.wordpress.org/oh-youtube-in-lightbox/trunk@843595 b8457f37-d9ea-0310-8a92-e5e31aec5664