Error on changing shopping list amounts.

[bk1984]

Whenever I try to change amounts in the shopping list I get this unrecoverable error:

System.ArgumentNullException: Value cannot be null. Parameter name: inner at System.Linq.Enumerable.Join[TOuter,TInner,TKey,TResult](IEnumerable1 outer, IEnumerable1 inner, Func2 outerKeySelector, Func2 innerKeySelector, Func3 resultSelector) at EDEngineer.Views.CommanderViewModel.HighlightShoppingListIngredient(List1 ingredients, Blueprint blueprint, Boolean highlighted) at EDEngineer.Views.MainWindow.ShoppingListBlueprintMouseLeave(Object sender, MouseEventArgs e) at System.Windows.Input.MouseEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget) at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target) at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs) at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised) at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args) at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e) at System.Windows.MouseOverProperty.FireNotifications(UIElement uie, ContentElement ce, UIElement3D uie3D, Boolean oldValue) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.FirePropertyChangeInAncestry(DependencyObject element, Boolean oldValue, DeferredElementTreeState treeState, Action2 originChangedAction) at System.Windows.ReverseInheritProperty.OnOriginValueChanged(DependencyObject oldOrigin, DependencyObject newOrigin, IList1 otherOrigins, DeferredElementTreeState& oldTreeState, Action`2 originChangedAction) at System.Windows.Input.MouseDevice.ChangeMouseOver(IInputElement mouseOver, Int32 timestamp) at System.Windows.Input.MouseDevice.PreNotifyInput(Object sender, NotifyInputEventArgs e) at System.Windows.Input.InputManager.ProcessStagingArea() at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input) at System.Windows.Input.MouseDevice.Synchronize() at System.Windows.Input.MouseDevice.OnHitTestInvalidatedAsync(Object sender, EventArgs e) at System.Windows.Input.InputManager.HitTestInvalidatedAsyncCallback(Object arg) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)