[v1.5.5] Transferwise trading with old client throws NPE

[ripcurlx]

Description

• Old client created a buy offer with TransferWise and new client takes it
• After payment received is clicked NPE was thrown in new client.

Feb.-01 10:24:42.818 [JavaFX Application Thread] INFO  b.d.m.p.p.s.s.SellerStep3View: User pressed the [Confirm payment receipt] button for Trade ngkpxbc 
Feb.-01 10:24:42.818 [JavaFX Application Thread] INFO  b.c.t.p.FluentProtocol$Condition: We received a PAYMENT_RECEIVED event at phase FIAT_SENT and state SELLER_RECEIVED_FIAT_PAYMENT_INITIATED_MSG, tradeId=ngkpxbc-69f8f84c-1488-4d6e-aa1c-9e38a498ad6e-154 
Feb.-01 10:24:42.818 [JavaFX Application Thread] INFO  bisq.core.trade.Trade: Set new state at SellerAsTakerTrade (id=ngkpxbc): SELLER_CONFIRMED_IN_UI_FIAT_PAYMENT_RECEIPT 
Feb.-01 10:24:42.819 [JavaFX Application Thread] ERROR bisq.common.setup.CommonSetup: Uncaught Exception from thread JavaFX Application Thread 
Feb.-01 10:24:42.819 [JavaFX Application Thread] ERROR bisq.common.setup.CommonSetup: throwableMessage= null 
Feb.-01 10:24:42.819 [JavaFX Application Thread] ERROR bisq.common.setup.CommonSetup: throwableClass= class java.lang.NullPointerException 
Feb.-01 10:24:42.823 [JavaFX Application Thread] ERROR bisq.common.setup.CommonSetup: Stack trace:
java.lang.NullPointerException
	at bisq.desktop.main.portfolio.pendingtrades.PendingTradesView.isMaybeInvalidTrade(PendingTradesView.java:319)
	at bisq.desktop.main.portfolio.pendingtrades.PendingTradesView.access$100(PendingTradesView.java:105)
	at bisq.desktop.main.portfolio.pendingtrades.PendingTradesView$1$1.update(PendingTradesView.java:588)
	at bisq.desktop.main.portfolio.pendingtrades.PendingTradesView$1$1.lambda$updateItem$0(PendingTradesView.java:573)

Ignoring the NPE the trade still can be completed.

I wasn't able to re-produce this in this exact setup, but I think it might be worth to add a safe-guard.