Uncaught mysqli_sql_exception: No such file or directory in system/library/db/mysqli.php:12

Stack trace:
#0 system/library/db/mysqli.php(12): mysqli->__construct()
#1 system/library/db.php(14): DB\MySQLi->__construct()
#2 system/framework.php(68): DB->__construct()
#3 system/startup.php(140): require_once('...')
#4 index.php(14): initialize()
#5 {main}
thrown in system/library/db/mysqli.php on line 12