DOUAudioPlaybackItem: Suppress a conversion warning.
DOUAudioPlaybackItem: Suppress a conversion warning.

Close #20.

QiuZhiFei/DOUAudioStreamer,douban/DOUAudioStreamer,jonesgithub/DOUAudioStreamer,talkmate/DOUAudioStreamer,cute/DOUAudioStreamer,zhantss/DOUAudioStreamer,xuanyi0627/DOUAudioStreamer,hjw6160602/DOUAudioStreamer,QiuZhiFei/DOUAudioStreamer,hjw6160602/DOUAudioStreamer,talkmate/DOUAudioStreamer,eyu1988/DOUAudioStreamer,NghiaTranUIT/DOUAudioStreamer,vinceee/DOUAudioStreamer,hjw6160602/DOUAudioStreamer,eyu1988/DOUAudioStreamer,NghiaTranUIT/DOUAudioStreamer,douban/DOUAudioStreamer,ycaihua/DOUAudioStreamer,zhouwude/DOUAudioStreamer,jonesgithub/DOUAudioStreamer,xuanyi0627/DOUAudioStreamer,ycaihua/DOUAudioStreamer,vinceee/DOUAudioStreamer,Learn-IOS/DOUAudioStreamer,zhantss/DOUAudioStreamer,sunfei/DOUAudioStreamer,zhouwude/DOUAudioStreamer,royalwang/DOUAudioStreamer,royalwang/DOUAudioStreamer,xuanyi0627/DOUAudioStreamer,sunfei/DOUAudioStreamer,Learn-IOS/DOUAudioStreamer,royalwang/DOUAudioStreamer,cute/DOUAudioStreamer,sunfei/DOUAudioStreamer,NghiaTranUIT/DOUAudioStreamer