Vote button doesn’t work – “NaN” in vote number

Hi, the vote button doesn’t work on the idea list on my website. the number of voters change to “NaN” when I click on the vote button on public board.

I can only vote on the idea post in administration, and in the idea details but not on idea list.

No message appears on the log console of Firefox/Chrome/IE

The page I need help with: [log in to see the link]