Uncaught exception: Undefined variable $_SESSION

Backtrace

( ! ) Fatal error: Uncaught ErrorException: A non-numeric value encountered in /var/web/xihe/application/toolkit/inc/dse/file.inc.php on line 245
( ! ) ErrorException: A non-numeric value encountered in /var/web/xihe/application/toolkit/inc/dse/file.inc.php on line 245
Call Stack
#	Time	Memory	Function	Location
1	0.0077	579696	Dse\Kit\Kit->exceptionHandler( $exception = class ErrorException { protected $message = 'Undefined variable $_SESSION'; private ${Exception}string = ''; protected $code = 2; protected $file = '/var/web/xihe/application/toolkit/inc/kit.class.php'; protected $line = 407; private array ${Exception}trace = [0 => [...], 1 => [...], 2 => [...], 3 => [...], 4 => [...], 5 => [...]]; private ?Throwable ${Exception}previous = NULL; protected $severity = 0; public $xdebug_message = '<tr><th align=\'left\' bgcolor=\'#f57900\' colspan="5"><span style=\'background-color: #cc0000; color: #fce94f; font-size: x-large;\'>( ! )</span> ErrorException: Undefined variable $_SESSION in /var/web/xihe/application/toolkit/inc/kit.class.php on line <i>407</i></th></tr>\n<tr><th align=\'left\' bgcolor=\'#e9b96e\' colspan=\'5\'>Call Stack</th></tr>\n<tr><th align=\'center\' bgcolor=\'#eeeeec\'>#</th><th align=\'left\' bgcolor=\'#eeeeec\'>Time</th><th align=\'left\' bgcolor=\'#eeeeec\'>Memory</th><th align=\'left\' bgcolor=\'#eeeeec'... } )	.../kit.class.php:0
2	0.0077	579776	Dse\Kit\Kit->internalError( $message = 'Uncaught exception: Undefined variable $_SESSION', $priority = 8, $filename = '/var/web/xihe/application/toolkit/inc/kit.class.php', $line_no = 407, $class_name = NULL, $backtrace = [0 => ['file' => '/var/web/xihe/application/toolkit/inc/kit.class.php', 'line' => 407, 'function' => 'errorHandler', 'class' => 'Dse\\Kit\\Kit', 'type' => '->'], 1 => ['file' => '/var/web/xihe/application/toolkit/inc/kit/security.class.php', 'line' => 117, 'function' => 'session', 'class' => 'Dse\\Kit\\Kit', 'type' => '->'], 2 => ['file' => '/var/web/xihe/application/toolkit/inc/kit.class.php', 'line' => 159, 'function' => 'check', 'class' => 'Dse\\Kit\\Security', 'type' => '->'], 3 => ['file' => '/var/web/xihe/application/toolkit/inc/kit.class.php', 'line' => 113, 'function' => 'init', 'class' => 'Dse\\Kit\\Kit', 'type' => '->'], 4 => ['file' => '/var/web/xihe/application/www/ini.php', 'line' => 26, 'function' => '__construct', 'class' => 'Dse\\Kit\\Kit', 'type' => '->'], 5 => ['file' => '/var/web/xihe/application/www/tool/log.php', 'line' => 178, 'args' => [...], 'function' => 'include']] )	.../kit.class.php:279
3	0.0110	581504	include( '/var/web/xihe/application/toolkit/template/dev-error.php )	.../kit.class.php:324
4	0.0113	582112	Dse\bytesize( $size = '2048M', $decimals = FALSE, $dec_point = ???, $thousands_sep = ???, $unit_sep = ??? )	.../dev-error.php:320
5	0.0113	582480	Dse\Kit\Kit->errorHandler( $error_no = 2, $message = 'A non-numeric value encountered', $filename = '/var/web/xihe/application/toolkit/inc/dse/file.inc.php', $line_no = 245 )	.../file.inc.php:245