iRobin were you successful at removing the polls extension via composer ? (composer remove reflar/polls). The uncaught class error is still present ?
Maybe the antivirus deleted some files in vendor, breaking the install. You could delete the vendor folder and run composer install in the Flarum folder to reinstall all dependencies. Before doing that make sure you have a file named composer.lock in your Flarum folder, this will ensure the exact same version of every dependency will be installed as before.
