fixed PHP error affecting some users

git-svn-id: https://plugins.svn.wordpress.org/progrids-widgets/trunk@918311 b8457f37-d9ea-0310-8a92-e5e31aec5664
version 1.5.8

git-svn-id: https://plugins.svn.wordpress.org/progrids-widgets/trunk@918314 b8457f37-d9ea-0310-8a92-e5e31aec5664