2178: Exception when changing tracks too fast

[TIV73]

Hey everyone,
when sequentially editing the same property of multiple tracks in fast succession while the property that's being changed is used for auto-sorting, it's possible to trigger a null reference exception.

I haven't yet figured out the exact steps to reproduce the issue, but from the looks of it, auto-sorting on a column happens live after a field was changed, and these view updates are being 'replayed' sequentially with a slight delay after the change was made.

It seems like editing a track prevents the view update from starting, but once the update started it will continue even if a new track is being changed at the moment. If changes are being made fast enough, the track that is being changed will update its index and once a new value is submitted, it causes a null pointer reference because the track that it references isn't there anymore.

To see it in action:
https://streamable.com/xggjg

Also see crash log C62E647C uploaded at around 19:49 on 2019-06-01.

[PetrCBR]

Thanks. Will check.