PHP error - strpos(): Empty needle

Hi,
after installing using a php file, the event log shows a php error all the time:

Error: strpos(): Empty needle at /lib/private/Template/SCSSCacher.php#516

The welcome window appears all the time and I cannot edit any information on the account or delete notifications.

mysql: 5.7.33

Error: strpos(): Empty needle at /lib/private/Template/SCSSCacher.php#516

<<closure>>

OC\Log\ErrorHandler::onError(2, "strpos(): Empty needle", "/lib/privat ... p", 516, { path: "/ap ... "})

/lib/private/Template/SCSSCacher.php - line 516:

strpos("/apps/settings/css", "")

/lib/private/Template/SCSSCacher.php - line 150:

OC\Template\SCSSCacher->getWebDir("/apps/settings/css", "settings", "", "")

/lib/private/Template/CSSResourceLocator.php - line 110:

OC\Template\SCSSCacher->process("/apps/settings", "css/settings.scss", "settings")

/lib/private/Template/CSSResourceLocator.php - line 85:

OC\Template\CSSResourceLocator->cacheAndAppendScssIfExist("/apps/settings", "css/settings.scss", "settings")

/lib/private/Template/ResourceLocator.php - line 78:

OC\Template\CSSResourceLocator->doFind("css/settings")

/lib/private/TemplateLayout.php - line 353:

OC\Template\ResourceLocator->find([ "css/serve ... "])

/lib/private/TemplateLayout.php - line 261:

OC\TemplateLayout::findStylesheetFiles([ "css/serve ... "])

/lib/private/legacy/OC_Template.php - line 182:

OC\TemplateLayout->__construct("user", "settings")

/lib/public/AppFramework/Http/TemplateResponse.php - line 204:

OC_Template->fetchPage({ forms: { p ... "})

/lib/private/AppFramework/Http/Dispatcher.php - line 171:

OCP\AppFramework\Http\TemplateResponse->render()

/lib/private/AppFramework/App.php - line 157:

OC\AppFramework\Http\Dispatcher->dispatch(OCA\Settings ... {}, "index")

/lib/private/Route/Router.php - line 302:

OC\AppFramework\App::main("OCA\\Settin ... r", "index", OC\AppFramew ... {}, { section: " ... "})

/lib/base.php - line 1006:

OC\Route\Router->match("/settings/admin/logging")

/index.php - line 36:

OC::handleRequest()