TypeError: Argument 1 passed to OCA\Files_FullTextSearch\Model\FilesDocument::setOwnerId() must be of the type string

Okay,

I open an other Ticket. I get this message when trying to index my files.

Nextcloud 15.0.0
PHP 7.2
Ubuntu 18.04
Nginx

An unhandled exception has been thrown: TypeError: Argument 1 passed to OCA\Files_FullTextSearch\Model\FilesDocument::setOwnerId() must be of the type string, boolean given, called in /var/www/cloud/apps/files_fulltextsearch/lib/Service/FilesService.php on line 289 and defined in /var/www/cloud/apps/files_fulltextsearch/lib/Model/FilesDocument.php:70 Stack trace: #0 /var/www/cloud/apps/files_fulltextsearch/lib/Service/FilesService.php(289): OCA\Files_FullTextSearch\Model\FilesDocument->setOwnerId(false) #1 /var/www/cloud/apps/files_fulltextsearch/lib/Service/FilesService.php(247): OCA\Files_FullTextSearch\Service\FilesService->generateFilesDocumentFromFile('Lars', Object(OC\Files\Node\Folder)) #2 /var/www/cloud/apps/files_fulltextsearch/lib/Service/FilesService.php(188): OCA\Files_FullTextSearch\Service\FilesService->getFilesFromDirectory('Lars', Object(OC\Files\Node\Folder)) #3 /var/www/cloud/apps/files_fulltextsearch/lib/Provider/FilesProvider.php(228): OCA\Files_FullTextSearch\Service\FilesService->getFilesFromUser('Lars', Object(OCA\FullTextSearch\Model\IndexOptions)) #4 /var/www/cloud/apps/fulltextsearch/lib/Service/IndexService.php(179): OCA\Files_FullTextSearch\Provider\FilesProvider->generateIndexableDocuments('Lars') #5 /var/www/cloud/apps/fulltextsearch/lib/Command/Index.php(407): OCA\FullTextSearch\Service\IndexService->indexProviderContentFromUser(Object(OCA\FullTextSearch_ElasticSearch\Platform\ElasticSearchPlatform), Object(OCA\Files_FullTextSearch\Provider\FilesProvider), 'Lars', Object(OCA\FullTextSearch\Model\IndexOptions)) #6 /var/www/cloud/apps/fulltextsearch/lib/Command/Index.php(271): OCA\FullTextSearch\Command\Index->indexProvider(Object(OCA\Files_FullTextSearch\Provider\FilesProvider), Object(OCA\FullTextSearch\Model\IndexOptions)) #7 /var/www/cloud/3rdparty/symfony/console/Command/Command.php(255): OCA\FullTextSearch\Command\Index->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #8 /var/www/cloud/core/Command/Base.php(166): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #9 /var/www/cloud/3rdparty/symfony/console/Application.php(946): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #10 /var/www/cloud/3rdparty/symfony/console/Application.php(248): Symfony\Component\Console\Application->doRunCommand(Object(OCA\FullTextSearch\Command\Index), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #11 /var/www/cloud/3rdparty/symfony/console/Application.php(148): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #12 /var/www/cloud/lib/private/Console/Application.php(213): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput)) #13 /var/www/cloud/console.php(96): OC\Console\Application->run() #14 /var/www/cloud/occ(11): require_once('/var/www/cloud/...')

Start at FilesService.php line 289, where generateFilesDocumentFromFile calls FilesDocument::setOwnerId, and inspect the method definition at FilesDocument.php line 70. Reproduce the failure through the indexing entry point shown in the stack trace and trace why a boolean reaches setOwnerId; done means file indexing completes without this TypeError.