Among the crimes with no arrest made, how many of them happened in the ward represented by alderman Pat Dowell?
no arrest has been made refers to arrest = 'FALSE'
SELECT SUM(CASE WHEN T1.alderman_last_name = 'Dowell' THEN 1 ELSE 0 END) FROM Ward AS T1 INNER JOIN Crime AS T2 ON T1.ward_no = T2.ward_no WHERE T2.arrest = 'FALSE' AND T1.alderman_first_name = 'Pat'