making subinventory field mandatory on inventory requisition

Hi All

I have made sandbox changes to make sub inventory field mandatory on Inventory requisitions but when i did this i am unable to do expense requisition. when i click save or submit or any action in expense requisition it is not working.

Sub inventory field should be mandatory on inventory requisition and while it is mandatory it should allow me to submit expense requisition.

Please let me know if anyone has done this

Thanks

Rama