Fix a Null Ref Exception...

src/AddIns/DisplayBindings/WpfDesign/WpfDesign.Designer/Project/Extensions/SnaplinePlacementBehavior.cs

@@ -227,7 +227,7 @@ namespace ICSharpCode.WpfDesign.Designer.Extensions
 			
 			foreach (var item in AllDesignItems() /* ExtendedItem.ContentProperty.CollectionElements */
 			         .Except(operation.PlacedItems.Select(f => f.Item))
-			         .Where(x=>!GetDisableSnaplines(x.View))) {
+			         .Where(x=> x.View != null && !GetDisableSnaplines(x.View))) {
 				if (item != null) {
 					var bounds = GetPosition(operation, item);