Launch in Limbo with BisqException when last navigation no longer exists

[niyid]

Description

I am not sure if this can happen to the general users, but it could happen fairly often to developers: while playing around with the navigation buttons, you may end up with a situation where the last navigation no longer exists. This renders the application inaccessible as a BisqException is thrown.

Version

1.2.0, 1.1.x

Steps to reproduce

1. Navigate to a particular screen then exit the application.
2. Go into the code and change the last navigation to something else so it no longer exists.
3. Rebuild the application and launch.

Expected behaviour

The last navigation no longer exists so the application navigates to a default path (for instance - MainView.class, MarketView.class, TradesChartsView.class).

Actual behaviour

A BisqException is thrown and the application launch never completes (stuck trying to load view).

Screenshots

Device or machine

Fedora 22 PC

Additional info

bisq.core.exceptions.BisqException: No button matching class bisq.desktop.main.offer.offerbook.OfferBookView found
	at bisq.desktop.main.MainView.lambda$initialize$6(MainView.java:385)
	at java.base/java.util.Optional.orElseThrow(Optional.java:397)
	at bisq.desktop.main.MainView.lambda$initialize$7(MainView.java:385)
	at bisq.desktop.Navigation.lambda$navigateTo$1(Navigation.java:140)
	at java.base/java.util.concurrent.CopyOnWriteArrayList.forEach(CopyOnWriteArrayList.java:804)
	at java.base/java.util.concurrent.CopyOnWriteArraySet.forEach(CopyOnWriteArraySet.java:425)
	at bisq.desktop.Navigation.navigateTo(Navigation.java:140)
	at bisq.desktop.Navigation.navigateToPreviousVisitedView(Navigation.java:155)
	at bisq.desktop.main.MainView.lambda$initialize$9(MainView.java:396)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:181)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.fireValueChangedEvent(BooleanPropertyBase.java:104)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:111)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
	at bisq.desktop.main.MainViewModel.onSetupComplete(MainViewModel.java:253)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1378)
	at bisq.core.app.BisqSetup.step5(BisqSetup.java:353)
	at bisq.core.app.BisqSetup.lambda$startP2pNetworkAndWallet$9(BisqSetup.java:571)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:181)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
	at javafx.base/javafx.beans.binding.ObjectBinding.invalidate(ObjectBinding.java:170)
	at javafx.base/com.sun.javafx.binding.BindingHelperObserver.invalidated(BindingHelperObserver.java:52)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
	at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.fireValueChangedEvent(BooleanPropertyBase.java:104)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:111)
	at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
	at bisq.core.app.P2PNetworkSetup$2.onDataReceived(P2PNetworkSetup.java:163)
	at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
	at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
	at bisq.network.p2p.P2PService.onDataReceived(P2PService.java:361)
	at bisq.network.p2p.peers.getdata.RequestDataManager$2.onComplete(RequestDataManager.java:339)
	at bisq.network.p2p.peers.getdata.RequestDataHandler.onMessage(RequestDataHandler.java:262)
	at bisq.network.p2p.network.NetworkNode.lambda$onMessage$4(NetworkNode.java:357)
	at java.base/java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
	at java.base/java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:658)
	at bisq.network.p2p.network.NetworkNode.onMessage(NetworkNode.java:357)
	at bisq.network.p2p.network.Connection.lambda$onMessage$5(Connection.java:429)
	at java.base/java.util.concurrent.CopyOnWriteArrayList.forEach(CopyOnWriteArrayList.java:804)
	at java.base/java.util.concurrent.CopyOnWriteArraySet.forEach(CopyOnWriteArraySet.java:425)
	at bisq.network.p2p.network.Connection.lambda$onMessage$6(Connection.java:429)
	at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(PlatformImpl.java:418)
	at java.base/java.security.AccessController.doPrivileged(Native Method)
	at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:417)
	at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
	at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
	at javafx.graphics/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(GtkApplication.java:277)
	at java.base/java.lang.Thread.run(Thread.java:844)