ERROR: Dispute's trade is null
Sometimes, there's peer who got external patches but disputes aren't closed on the GUI, it leaves error like this when trying to close the dispute and the app crashes
```
[JavaFX Application Thread] WARN  h.d.m.s.d.a.a.ArbitratorView: Dispute's trade is null for trade {scrubbed-trade-id}
```
Closing trades when trades/disputes are 'null' could fix that