Borbole is right, you are missing a comumn in the forum table, you can add this in PHPMyadmin. The reason for the error having a 3.8.0 tag on it is because the DB was 1st populated with a 3.8.0 install, its really not too important, but you will need to fix that table.
Once it is fixed you will need to run some maintenance tasks in the admin cp, rebuild thread and post information.
Then run the DB check and repair tool, then run the Unique Indexes fix as well. You need to do this so every thing works correctly.
If you dont know how to use PHPMyAdmin on your DB, get someone who does to fix that table for you!!