ha_tokudb.so not found … but TokuDB is not installed

I found following message in /var/log/mysql.err and I would like to find out how to remove it (as it disturbs me a bit): 2019-12-01 8:13:40 140640051248512 [ERROR] Can’t open shared library ‘/usr/lib/x86_64-linux-gnu/mariadb18/plugin/ha_tokudb.so’ (errno: 0, cannot open shared object file: No such file or directory) Long time ago, I had tested TokuDB, but uninstalled it again.…