Ensure pointers aren't used anymore when their parents are being deleted and they should be deleted themselves.

PkmnLibSharp/Library/Items/ItemLibrary.cs

@@ -63,6 +63,15 @@ namespace PkmnLibSharp.Library.Items
         {
         }
 
+        protected internal override void MarkAsDeleted()
+        {
+            base.MarkAsDeleted();
+            foreach (var item in _cache)
+            {
+                item.Value.MarkAsDeleted();
+            }
+        }
+
         protected override void DeletePtr()
         {
             Creatureliblibrary.Generated.ItemLibrary.Destruct(Ptr);