The function addKYCAddressViaSignature in KYCRegistry.sol is restricted to the KYC requirement group, which is allowed to give KYC status to users addresses. Considering the KYC status is checked all over the protocol and if KYCed the zero address can be used. A check should be made in the function addKYCAddressViaSignature to make sure
the KYC status isnt given to the zero address.
Add this check to the function addKYCAddressViaSignature:
