Ok so as I see it there are (possibly) 3 bugs here:
1) it added the torrent to your dock when you dragged it to trash - this might not be a bug, you might have accidentally added it to the dock and then when it failed to delete you dragged a 2nd time and actually trashed it - please try to confirm/deny this
2) a file that was added to the dock was later deleted, but still shows up in the dock
3) it crashes when trying to open a file that doesnt exist (somewhat related to #2, but slightly different)
Ok so as I see it there are (possibly) 3 bugs here:
1) it added the torrent to your dock when you dragged it to trash - this might not be a bug, you might have accidentally added it to the dock and then when it failed to delete you dragged a 2nd time and actually trashed it - please try to confirm/deny this
2) a file that was added to the dock was later deleted, but still shows up in the dock
3) it crashes when trying to open a file that doesnt exist (somewhat related to #2, but slightly different)