WARSAW, Dec. 23 (Delayed). (p—Count Andre Potocki, a mem ber of one of Poland's oldest and proudest families, was sentenced to eight years imprisonment today following his conviction on charges of trying to smuggle his family's art treasures out of the country. His dark-haired bride, Countess Maia Potocki, was sentenced to six years imprisonment. The pair was arrested last Oc tober by security police, who said they were loading priceless works of art into trucks at night. Polish law forbids the export of art ob jects. A tribunal at Krakow, mean while, acquitted the Polish writer Stanislaw Wasilewski of charges of collaborating with the Nazis during the German occupation.