Removing all columns throws exception by Bronwyn McNutt

If you have three or more columns open, and you close them all, Vancouver throws an exception. Just having one or two columns up and then closed doesn't throw.

[Arg_NullReferenceException]
Arguments:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=4.0.50524.0&File=mscorlib.dll&Key=Arg_NullReferenceException

at Microsoft.Vancouver.Silverlight.Common.Helpers.ItemsControlHelper.ScrollHome(FrameworkElement element)
at Microsoft.Vancouver.Silverlight.Main.Controls.NuggetColumnList.ScrollTo(Int32 columnIndex)
at Microsoft.Vancouver.Silverlight.Main.Controls.NuggetColumnList.OnFirstItemChanged(DependencyPropertyChangedEventArgs e)
at Microsoft.Vancouver.Silverlight.Main.Controls.NuggetColumnList.OnFirstItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
at System.Windows.DependencyObject.RaisePropertyChangeNotifications(DependencyProperty dp, Object oldValue, Object newValue)
at System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
at System.Windows.DependencyObject.RefreshExpression(DependencyProperty dp)
at System.Windows.Data.BindingExpression.SendDataToTarget()
at System.Windows.Data.BindingExpression.SourcePropertyChanged(PropertyPathListener sender, PropertyPathChangedEventArgs args)
at System.Windows.PropertyPathListener.RaisePropertyPathStepChanged(PropertyPathStep source)
at System.Windows.PropertyAccessPathStep.RaisePropertyPathStepChanged(PropertyListener source)
at System.Windows.CLRPropertyListener.SourcePropertyChanged(Object sender, PropertyChangedEventArgs args)
at System.Windows.Data.WeakPropertyChangedListener.PropertyChangedCallback(Object sender, PropertyChangedEventArgs args)
at System.ComponentModel.PropertyChangedEventHandler.Invoke(Object sender, PropertyChangedEventArgs e)
at Microsoft.Vancouver.Silverlight.Common.BaseNotifyPropertyChanged.OnPropertyChanged(String propertyName)
at Microsoft.Vancouver.Silverlight.Main.ViewModels.ClientColumnListViewModel.set_FirstItem(Int32 value)
at Microsoft.Vancouver.Silverlight.Main.ViewModels.ClientColumnListViewModel.CleanUpDeletedColumn(ClientColumnConfiguration clientColumnconfiguration, Boolean isAttached)
at Microsoft.Vancouver.Silverlight.Main.ViewModels.ClientColumnListViewModel.<>c__DisplayClass6.<DeleteColumn>b__4(DataServiceResponseResult response)
at Microsoft.Vancouver.Silverlight.Main.Service.VancouverRepository.<>c__DisplayClass69.<>c__DisplayClass6b.<SaveChanges>b__68()