CDB3-2231 Can not activate prolongation for award[0]

Steps To Reproduce:
1.Publish DGF procedure
2.Publish and activate bids
3.Wait until the end of auction
4.Create prolongation for award[0]
5.Activate prolongation for award[0]

Actual result:
500 error

Expected result:
Response 200 {"message": "ok"}

For award[1] - prolongation activates correctly
https://procedure-dev.prozorro.sale/api/procedures/61a4925e7640435b0753c71e