Fix forcetab for plugins



git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@22987 35612d4c-9d10-0410-837c-bf9dd1be60d7
ensure login/password are not empty

git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@22988 35612d4c-9d10-0410-837c-bf9dd1be60d7