Exception FilesService calling `$document->getContent()` while indexing a Document

I have a new Debian 10 installation with Nextcloud 20.0.3.

Running occ fulltextsearch:index leads to an unhandled exception:

An unhandled exception has been thrown:
Error: Call to a member function getContent() on string in /var/www/html/nextcloud/apps/files_fulltextsearch/lib/Service/FilesService.php:719
Stack trace:
#0 /var/www/html/nextcloud/apps/files_fulltextsearch/lib/Service/FilesService.php(658): OCA\Files_FullTextSearch\Service\FilesService->updateContentFromFile('*** sensitive p...', Object(OC\Files\Node\File))
#1 /var/www/html/nextcloud/apps/files_fulltextsearch/lib/Service/FilesService.php(638): OCA\Files_FullTextSearch\Service\FilesService->updateFilesDocumentFromFile(Object(OCA\Files_FullTextSearch\Model\FilesDocument), Object(OC\Files\Node\File))
#2 /var/www/html/nextcloud/apps/files_fulltextsearch/lib/Service/FilesService.php(529): OCA\Files_FullTextSearch\Service\FilesService->updateFilesDocument(Object(OCA\Files_FullTextSearch\Model\FilesDocument))
#3 /var/www/html/nextcloud/apps/files_fulltextsearch/lib/Provider/FilesProvider.php(268): OCA\Files_FullTextSearch\Service\FilesService->generateDocument(Object(OCA\Files_FullTextSearch\Model\FilesDocument))
#4 /var/www/html/nextcloud/apps/fulltextsearch/lib/Service/IndexService.php(317): OCA\Files_FullTextSearch\Provider\FilesProvider->fillIndexDocument(Object(OCA\Files_FullTextSearch\Model\FilesDocument))
#5 /var/www/html/nextcloud/apps/fulltextsearch/lib/Service/IndexService.php(204): OCA\FullTextSearch\Service\IndexService->indexDocuments(Object(OCA\FullTextSearch_Elasticsearch\Platform\ElasticSearchPlatform), Object(OCA\Files_FullTextSearch\Provider\FilesProvider), Array, Object(OCA\FullTextSearch\Model\IndexOptions))
#6 /var/www/html/nextcloud/apps/fulltextsearch/lib/Command/Index.php(410): OCA\FullTextSearch\Service\IndexService->indexProviderContentFromUser(Object(OCA\FullTextSearch_Elasticsearch\Platform\ElasticSearchPlatform), Object(OCA\Files_FullTextSearch\Provider\FilesProvider), 'Andy', Object(OCA\FullTextSearch\Model\IndexOptions))
#7 /var/www/html/nextcloud/apps/fulltextsearch/lib/Command/Index.php(273): OCA\FullTextSearch\Command\Index->indexProvider(Object(OCA\Files_FullTextSearch\Provider\FilesProvider), Object(OCA\FullTextSearch\Model\IndexOptions))
#8 /var/www/html/nextcloud/3rdparty/symfony/console/Command/Command.php(255): OCA\FullTextSearch\Command\Index->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#9 /var/www/html/nextcloud/core/Command/Base.php(169): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#10 /var/www/html/nextcloud/3rdparty/symfony/console/Application.php(1000): OC\Core\Command\Base->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#11 /var/www/html/nextcloud/3rdparty/symfony/console/Application.php(271): Symfony\Component\Console\Application->doRunCommand(Object(OCA\FullTextSearch\Command\Index), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#12 /var/www/html/nextcloud/3rdparty/symfony/console/Application.php(147): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#13 /var/www/html/nextcloud/lib/private/Console/Application.php(215): Symfony\Component\Console\Application->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#14 /var/www/html/nextcloud/console.php(100): OC\Console\Application->run()
#15 /var/www/html/nextcloud/occ(11): require_once('/var/www/html/n...')

Are there any possibilities to fix that error?

Reproduce the failure with occ fulltextsearch:index, then inspect apps/files_fulltextsearch/lib/Service/FilesService.php around lines 638, 658, and 719. Trace the value passed to updateContentFromFile() from the FilesProvider indexing path. Done means indexing no longer throws the reported getContent() exception.