Database can't save connect instances because var "$group" default is NULL

[s524797336]

See system/Database/Config.php line 82 and 108

If we always use
$this->db = \Config\Database::connect();
To connect db
`//line 82
if ($getShared && isset(self::$instances[$group]))
{
return self::$instances[$group];
}
//other code

//line 108
self::$instances[$group] =& $connection;`
This code will never save instance because $group is NULL