[r21839]GrampsLocale: Fix NoneType error

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21840 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
updated dutch translation

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21842 4ae1f11a-8b86-4847-b8af-ab372f36d1fd