Fix reference to NULL pointer when there are no playmarks
Fix reference to NULL pointer when there are no playmarks

ace20022/libbluray,tourettes/libbluray,Azzuro/libbluray,ShiftMediaProject/libbluray,Azzuro/libbluray,tourettes/libbluray,zxlooong/libbluray,UIKit0/libbluray,pingflood/libbluray,zxlooong/libbluray,ace20022/libbluray,UIKit0/libbluray,EdwardNewK/libbluray,EdwardNewK/libbluray,Azzuro/libbluray,EdwardNewK/libbluray,Distrotech/libbluray,Azzuro/libbluray,vlc-mirror/libbluray,mwgoldsmith/bluray,koying/libbluray,Distrotech/libbluray,vlc-mirror/libbluray,ShiftMediaProject/libbluray,ace20022/libbluray,koying/libbluray,pingflood/libbluray,pingflood/libbluray,EdwardNewK/libbluray,UIKit0/libbluray,koying/libbluray,Distrotech/libbluray,vlc-mirror/libbluray,ace20022/libbluray,zxlooong/libbluray,tourettes/libbluray,mwgoldsmith/bluray,koying/libbluray,ShiftMediaProject/libbluray,vlc-mirror/libbluray,mwgoldsmith/bluray,UIKit0/libbluray,ShiftMediaProject/libbluray,Distrotech/libbluray,mwgoldsmith/bluray,tourettes/libbluray