For years(~2014), I've had a macOS Terminal app that reads and analyzes a *.mov file frame by frame. When I updated from macOS 10.13.3 to 10.14.1, it started crashing. When I began debugging, I found that an AVAssetTrack which I had extracted from an AVURLAsset, previously kept a reference to that Asset in the track.asset variable, but now had nil for its track.asset. Should I have retained the AVURLAsset? Or what?