Error 500 after upgrade to 2.3.5

Hello,
after upgrading from version 2.3.2 to version 2.3.5,
the admin area works. In the frontend I receive the following message:

 

1 exception(s):
Exception #0 (Exception): Notice: Trying to access array offset on value of type null in xxxx/vendor/magento/framework/App/AreaList.php on line 78

Exception #0 (Exception): Notice: Trying to access array offset on value of type null in xxxx/vendor/magento/framework/App/AreaList.php on line 78
<pre>#1 MagentoFrameworkAppAreaList->getCodeByFrontName() called at [vendor/magento/framework/App/Http.php:111]
#2 MagentoFrameworkAppHttp->launch() called at [generated/code/Magento/Framework/App/Http/Interceptor.php:24]
#3 MagentoFrameworkAppHttpInterceptor->launch() called at [vendor/magento/framework/App/Bootstrap.php:261]
#4 MagentoFrameworkAppBootstrap->run() called at [index.php:39]
</pre>

after installation I ran the following commands:

 

rm -rf var/cache/* var/view_preprocessed/* generated/* pub/static/*
php bin/magento setup:upgrade
php bin/magento setup:di:compile
php bin/magento setup:static-content:deploy -f
php bin/magento indexer:reindex
php bin/magento cache:flush

 

The php version is 7.2.
The theme set is luma.

 

Thanks in advance!

 

Carlo