MM- outbound delivery through Stock Transport order

How to stop the automatic creation of outbound delivery for a stock transport order(STO), in Txn ME21N. Actually after save of a transfer order of STO type, when we try to create the outbound delivery in Txn->VL10B, in background, It creates the delivery, without checking the stock in the storage location. This creates further problem in Picking. So the outbound delivery should not be created for those materials which do not have proper stock within correct storage location.

If any one has faced it, please help me in writing user exit or any other method to validate the same.