Two things you can try:
Clear the cache ( and/or delete the directories shop-root/var/cache/prod or shop-root/var/cache/dev). This might be enough to fix it.
Failing that you could disable/remove that free 3rd party module (gaffiliatemarketingfree) and see if that fixes it. If you can't access the modules menu option in the back office, then you'll need to backup and delete the module directory via ftp. With most minor upgrades you can get away with leaving 3rd-party modules enabled but not always.