After Update the Plugin to 8721 the complete backend broke:
"The source code of 'Multilanguage HTML Widget' plugin was updated. Need to update plugin DB."  
Clicked on Update, an exception is thrown:
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to UPDATE_ErrorManager::exceptionHandler() must be an instance of Exception, instance of TypeError given in /var/www/vhosts/domain.de/httpdocs/ow_updates/classes/error_manager.php:190, referer: https://www.domain.de/...i=admin%2FusersStack trace:, referer: https://www.domain.de/...ck_uri=admin%2Fusers[internal function]: UPDATE_ErrorManager->exceptionHandler(Object(TypeError)), referer: https://www.domain.de/...ck_uri=admin%2Fusers {main}, referer: https://www.domain.de/...=admin%2Fusersthrown in /var/www/vhosts/domain.de/httpdocs/ow_updates/classes/error_manager.php on line 190, referer: https://www.domain.de/...ck_uri=admin%2Fusers