VLCLibrary: don't nil instance variable
VLCLibrary: don't nil instance variable

This is evil as libvlc_release is async

CollabraMusic/VLCKit,siuying/VLCKit,siuying/VLCKit,simon1984/test,larrytin/VLCKit,simon1984/test,kamcord/VLCKit,kamcord/VLCKit,hpsoar/VLCKit,CollabraMusic/VLCKit,CollabraMusic/VLCKit,waterskier2007/VLCKit,programming086/VLCKit,siuying/VLCKit,i386/vlckit,hpsoar/VLCKit,simon1984/test,waterskier2007/VLCKit,larrytin/VLCKit,strukturag/VLCKit,waterskier2007/VLCKit,strukturag/VLCKit,kamcord/VLCKit,brion/VLCKit,programming086/VLCKit