Make model manager in `DownloadTrackingComposite` protected
Make model manager in `DownloadTrackingComposite` protected

NeoAdonis/osu,peppy/osu-new,smoogipooo/osu,UselessToucan/osu,peppy/osu,NeoAdonis/osu,peppy/osu,peppy/osu,NeoAdonis/osu,ppy/osu,ppy/osu,UselessToucan/osu,smoogipoo/osu,smoogipoo/osu,ppy/osu,smoogipoo/osu,UselessToucan/osu