Polyang 2.0.5, error since update

Hi,

since the last update to 2.0.5 I get two errors, that disappear when disabling polylang. For now I went back to version 2.0.4.
Is this a problem with polylang itself, i.e. will be solved with the next update, or a bug in my installation?

Thanks, regards
Martin

Details:
One error is shown on every admin page:
“Warning: md5() expects parameter 1 to be string, array given in /home/.sites/102/site6674223/web/wp-content/plugins/polylang/admin/admin-strings.php on line 41 Warning: md5() expects parameter 1 to be string, array given in /home/.sites/102/site6674223/web/wp-content/plugins/polylang/admin/admin-strings.php on line 41”

$to_register = compact( ‘name’, ‘string’, ‘context’, ‘multiline’ );
if ( ! in_array( $to_register, self::$strings ) && $to_register[‘string’] ) {
self::$strings[ md5( $string ) ] = $to_register;

the last line being line 41.

Just for a little bit on context that could help: It also affects registration of new users with the plugin usersultra, giving me a the error upon attempt to register with existing email: “Catchable fatal error: Object of class WP_Error could not be converted to string in /home/.sites/102/site6674223/web/wp-content/plugins/users-ultra-pro/addons/groups/admin/admin.php on line 338 at <a”
or simply telling “already registered” with a new email.

Lines 337-339
//check if already added to the group
$sql = ‘ SELECT * FROM ‘ . $wpdb->prefix . ‘usersultra_groups_users_groups_rel WHERE group_user_group_rel_user_id= “‘.$user_id.'” AND group_user_group_rel_group_id= “‘.$group_id.'” ‘ ;
$res = $wpdb->get_results($sql);