Contrary to the key invariants stated in the README (After maturity, wrapped fCash can no longer be minted.), matured fCash can be sent to this wfCash contract to receive wrapped fCash tokens in return.
https://github.com/code-423n4/2022-06-notional-coop/blob/6f8c325f604e2576e2fe257b6b57892ca181509a/notional-wrapped-fcash/contracts/wfCashLogic.sol#L107-L152
Consider adding a check for fCash maturity:
