Inventory Location on Split Lines

When we have sales orders for certain customers that we want to make sure that they get inventory that we have in stock, we'll set the location on the sales order.  If there isn't enough inventory to fulfill the order, the line will split and the location will be copied to the split line.  Since there will be no inventory left in that location, the location remains on that line and it awaits inventory.  Other orders are able to be fulfilled ahead of one with the designated location.

I'd like to know if there is a way to have the line generated without a location.  If that's not an option, I'd like to know if there is a module that can clear the location if there is no inventory in a location.