Field value cannot be emptied in Configure Plugin: TEI Display

[tjnurmin]

• if you have filled in a field, it cannot be emptied
• however, if you input - there, that DC element is no longer imported

[tjnurmin]

There should be

if ($val && $val !== get_plugin_ini('TeiDisplay', $key) || $val == '') {
    set_option($key, $val);
}

on line 83 in models/TeiDisplayTextTable.php