DB: fix memory leak
DB: fix memory leak

SleimanJneidi/mapdb,lamfire/mapdb,binarytemple/mapdb,codeaudit/mapdb,cocosli/mapdb,jankotek/mapdb,pettermahlen/mapdb,sumit784/mapdb,jankotek/MapDB,ringoluo/mapdb,hangum/mapdb,ffjiao/mapdb,jankotek/mapdb,morfeo8marc/mapdb,jankotek/MapDB