JDBC Realm (Elytron) - attribute mappings cannot be removed from configuration

When opening
Configuration => Subsystems => Configuration => Security (Elytron) => Security Realms => JDBC Realm => Principal Query
the field "Attribute Mapping" shows only the first attribute

via cli this looks correct

/subsystem=elytron/jdbc-realm=MySqlJDBCRealm:read-resource
{
"outcome" => "success",
"result" => {"principal-query" => [{
"sql" => "SELECT u.password, r.role FROM users u, roles r WHERE u.username =? AND u.username = r.username",
"data-source" => "MySQLTestDS",
"attribute-mapping" => [

],
"clear-password-mapper" =>

}]}
}