0 Call to undefined method Joomla\CMS\Application\SiteApplication::isAdmin()

-- HikaShop version -- : 4.7.2.
-- Joomla version -- : 4.2.9
-- PHP version -- : 8.0.27
-- Browser(s) name and version -- : Brave latest
-- Error-message(debug-mod must be tuned on) -- : 0
Call to undefined method Joomla\CMS\Application\SiteApplication::isAdmin()

Call stack
# Function Location
1 () JROOT/media/com_hikashop/mail/order_creation_notification.preload.modified.php:62
2 include() JROOT/administrator/components/com_hikashop/classes/mail.php:362
3 hikashopMailClass->loadEmail() JROOT/administrator/components/com_hikashop/classes/mail.php:31
4 hikashopMailClass->get() JROOT/administrator/components/com_hikashop/classes/order.php:2075
5 hikashopOrderClass->loadOrderNotification() JROOT/administrator/components/com_hikashop/classes/order.php:442
6 hikashopOrderClass->save() JROOT/administrator/components/com_hikashop/classes/order.php:913
7 hikashopOrderClass->createFromCart() JROOT/components/com_hikashop/controllers/checkout.php:674
8 checkoutController->confirm() JROOT/libraries/src/MVC/Controller/BaseController.php:672
9 Joomla\CMS\MVC\Controller\BaseController->execute() JROOT/administrator/components/com_hikashop/helpers/helper.php:2437
10 hikashopController->execute() JROOT/components/com_hikashop/hikashop.php:88
11 require_once() JROOT/libraries/src/Dispatcher/LegacyComponentDispatcher.php:71
12 Joomla\CMS\Dispatcher\LegacyComponentDispatcher::Joomla\CMS\Dispatcher\{closure}() JROOT/libraries/src/Dispatcher/LegacyComponentDispatcher.php:73
13 Joomla\CMS\Dispatcher\LegacyComponentDispatcher->dispatch() JROOT/libraries/src/Component/ComponentHelper.php:355
14 Joomla\CMS\Component\ComponentHelper::renderComponent() JROOT/libraries/src/Application/SiteApplication.php:208
15 Joomla\CMS\Application\SiteApplication->dispatch() JROOT/libraries/src/Application/SiteApplication.php:249
16 Joomla\CMS\Application\SiteApplication->doExecute() JROOT/libraries/src/Application/CMSApplication.php:294
17 Joomla\CMS\Application\CMSApplication->execute() JROOT/includes/app.php:61
18 require_once() JROOT/index.php:32

Hello support,
I have made the upgrade to joomla 4 all seem to work fine.
But in the last step in the checkout, the moment leaving the website to the payment provider i got an error.
0 Call to undefined method Joomla\CMS\Application\SiteApplication::isAdmin()


I use the mollie skysider plugin.

I don't know how to solve this.

Thanks in advance
regards WJ

I found the solution for this error.
There were some overides in the SYSTEM -> E-mails.
When removing those al seem to work fine.
Sorry for bothering.
Regards Wim