require(!((_value != 0) && (allowed[msg.sender][_spender] != 0)));
// Optimizing lookup
address transferProxy = address(ASTARIA_ROUTER.TRANSFER_PROXY());

// If existing approval is non-zero -> set it to zero
if (ERC20(paymentToken).allowance(address(this), transferProxy) != 0) {
    ERC20(paymentToken).safeApprove(transferProxy, 0);
}

// Set non-zero approval
ERC20(paymentToken).safeApprove(transferProxy, payment - liquidatorPayment);
