My apologies for not responding earlier. Normally I get SMS alerts for new bugs, but not this time.
It sounds like you have a BB-Code named "CAT" which has the vw_category_tag identifier but is not associated with the VaultWiki add-on. This should not be possible and suggests a leftover side effect from some problem you may have had in the past. If you are not aware of how the data originally got this way, there is little we can do from the software side, since no one else has had an issue like this when upgrading.
You should manually change the CAT BB-Code's add-on assignment to VaultWiki via XenForo's BB-Code manager. Then attempt the upgrade again.