Log better error when trying to access out of bounds value on C# list

Upsilon/BaseTypes/UserData/ListUserData.cs

@@ -62,6 +62,12 @@ namespace Upsilon.BaseTypes.UserData
             {
                 return null;
             }
+
+            if (i < 0 || i >= List.Count)
+            {
+                diagnostics.LogError($"Index out of bounds, index: '{i}'", span);
+                return new ScriptNull();
+            }
             return List[i].ToScriptType();
         }