Guard statements when accessing first call of an account with identifier

AccountPhoneCallGuard.swift

func hangUpFirstCallOnAccountWithIdentifier(identifier: Int) {
    guard let account = accountRegistry.accountWithIdentifier(identifier) else  {
        print("Could not find account")
        return
    }
    guard let call = account.firstCall else {
        print("Could not find first call for an account")
        return
    }
    call.hangUp()
}