In llMessageLinked() use GetInventoryItems() rather than cloning TaskInventory directory

GetInventoryItems() returns a new list and so is equivalent, and creates this list under lock whereas Clone() is not thread-safe

OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs

@@ -4333,9 +4333,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             UUID partItemID;
             foreach (SceneObjectPart part in parts)
             {
-                TaskInventoryDictionary itemsDictionary = (TaskInventoryDictionary)part.TaskInventory.Clone();
-
-                foreach (TaskInventoryItem item in itemsDictionary.Values)
+                foreach (TaskInventoryItem item in part.Inventory.GetInventoryItems())
                 {
                     if (item.Type == ScriptBaseClass.INVENTORY_SCRIPT)
                     {