add more checks to avoid notice see #4496


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21801 35612d4c-9d10-0410-837c-bf9dd1be60d7
minor clean


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21803 35612d4c-9d10-0410-837c-bf9dd1be60d7