[0.84] Fix use Dropdown::showYesNo in slalevel

git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21434 35612d4c-9d10-0410-837c-bf9dd1be60d7
minor fix


git-svn-id: https://forge.indepnet.net/svn/glpi/trunk@21436 35612d4c-9d10-0410-837c-bf9dd1be60d7