Adding New Forum: "Internal error processing your request..."

I saw a mention of this bug on a 5.x issue. Since this is 6.x, I'm opening a new issue.

Basically, it was as it was described in the other issue - a user who has privileges of "Moderator" and can create new forums is running into this error:

"Internal error processing your data. Please contact website administrators"

Is there a patch for this?

Thanks!