Stop DevTools crashing when tree changed.

PerspexReadOnlyListView had some problems...

Perspex.Base/Collections/PerspexReadOnlyListView.cs

@@ -115,14 +115,14 @@ namespace Perspex.Collections
                     case NotifyCollectionChangedAction.Add:
                         ev = new NotifyCollectionChangedEventArgs(
                             NotifyCollectionChangedAction.Add,
-                            e.NewItems,
+                            e.NewItems.Cast<object>().ToList(),
                             e.NewStartingIndex);
                         break;
                     case NotifyCollectionChangedAction.Remove:
                         ev = new NotifyCollectionChangedEventArgs(
                             NotifyCollectionChangedAction.Remove,
                             e.OldItems,
-                            e.NewStartingIndex);
+                            e.OldStartingIndex);
                         break;
                     case NotifyCollectionChangedAction.Replace:
                         ev = new NotifyCollectionChangedEventArgs(
@@ -248,7 +248,7 @@ namespace Perspex.Collections
             return this.GetEnumerator();
         }
 
-        private IList<TOut> ConvertList(IEnumerable list)
+        private IList ConvertList(IEnumerable list)
         {
             return list.Cast<TIn>().Select(this.convert).ToList();
         }
@@ -271,7 +271,7 @@ namespace Perspex.Collections
                         ev = new NotifyCollectionChangedEventArgs(
                             NotifyCollectionChangedAction.Remove,
                             this.ConvertList(e.OldItems),
-                            e.NewStartingIndex);
+                            e.OldStartingIndex);
                         break;
                     case NotifyCollectionChangedAction.Replace:
                         ev = new NotifyCollectionChangedEventArgs(