TYPO3 Core

Hello,

I'm just upgrading a project from TYPO3 8 to TYPO3 9. After upgrading TYPO3s SourceCode I visit the TYPO3 Backend. But with this request the LocalConfiguration.php was updated silently. All my individual Configuration in extConf were thrown away and replaced with the default values of ext_conf_template.txt.
I mentioned this problem a little bit too late and started a new try to upgrade, but that time I visit the Installtool first. Now, the extConf values were transferred correctly into new EXTENSIONS key of LocalConfiguration.php.

Installtool calls "executeSilentLegacyExtConfExtensionConfigurationUpdateAction" which does the correct job.

First request to BE calls ExtensionConfiguration->synchronizeExtConfTemplateWithLocalConfigurationOfAllExtensions which creates EXTENSIONS key with default values. It seems that this line makes the problem:
$currentLocalConfiguration = $GLOBALS['TYPO3_CONF_VARS']['EXTENSIONS'] ?? [];

Stefan