Tell the number of cases with arrests in North Lawndale community.
number of cases refers to count(case_number); arrest refers to arrest = 'TRUE'; North Lawndale community refers to community_area_name = 'North Lawndale'
SELECT SUM(CASE WHEN T1.community_area_name = 'North Lawndale' THEN 1 ELSE 0 END) FROM Community_Area AS T1 INNER JOIN Crime AS T2 ON T1.community_area_no = T2.community_area_no WHERE T2.arrest = 'TRUE'