Transaction Response with no fee attribute when fee = 0

_**I'll repost the same topic as done a few days ago on the algorand forum [here](https://forum.algorand.org/t/transaction-response-with-no-fee-attribute-when-fee-0/14218/1)_

Hi everyone!
In my Java backend, when retrieving txn information with the indexer client, i find out that the chain response with all params of a txn with fee = 0 (because of part of a txn group where just one txn pays fees for all txns in the group) doesn’t cointain the param fee itself. For this reason, the java algorand sdk parses the response and sets the fee as Account.MIN_TX_FEE_UALGOS. So, there’s no way to discriminate between 0 fee txn and a MinFee one.
Is there a reason to this behaviour?

Thank you in advance!