Bro...need help too...on this... 
after update got also this error when i click nominate button at my postbit_legacy setting
note: Tried also
Clean Install (delete thread and upload all new files same as product...) but still no luck!
new
functions_nominate_topic.php 3X test to upload
Database error in vBulletin 3.6.8:
but you can see the nominated topic to poll thread
+++++++++++++++++++++
got (3) of this also:
Withdraw All Nominations < not working to poll
Withdraw All Nominations < not working to poll
Withdraw Your Nomination < working good
thanks and best regards...