In 2012, how many complaints about Credit card product came from clients in Omaha?
in 2012 refers to Date received LIKE'2012%'; in Omaha refers to city = 'Omaha'
SELECT COUNT(T1.client_id) FROM client AS T1 INNER JOIN events AS T2 ON T1.client_id = T2.Client_ID WHERE T1.city = 'Omaha' AND strftime('%Y', T2.`Date received`) = '2012' AND T2.Product = 'Credit card'