Check condition before calling NestedFactory._handleUnderSpending

[code423n4]

Handle

hyh

Vulnerability details

Impact

Whenever condition of the _handleUnderSpending function fails function call gas costs are wasted. The cost of checking the condition is paid anyway, while when it doesn't hold the function call costs are avoidable.

Proof of Concept

_handleUnderSpending checks for _amountToSpent - _amountSpent > 0.
https://github.com/code-423n4/2021-11-nested/blob/main/contracts/NestedFactory.sol#L481

Recommended Mitigation Steps

When the check condition is false _handleUnderSpending shouldn't be called and this way the check with corresponding variables to be placed in caller functions:

_submitInOrders
https://github.com/code-423n4/2021-11-nested/blob/main/contracts/NestedFactory.sol#L306

_safeSubmitOrder
https://github.com/code-423n4/2021-11-nested/blob/main/contracts/NestedFactory.sol#L415