Prevent exception if inventory item in llGiveInventory() call doesn't exist.

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

@@ -4104,6 +4104,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
             if (item == null)
             {
                 Error("llGiveInventory", "Can't find inventory object '" + inventory + "'");
+                return;
             }
 
             UUID objId = item.ItemID;