getInterestOverdue reverts rather than returning 0 when there is no overdue interest

[code423n4]

Handle

TomFrenchBlockchain

Vulnerability details

Impact

Potentially unexpected reverts when being called by external code

Proof of Concept

Here we revert if there's no extension (and therefore no overdue interest)

https://github.com/code-423n4/2021-12-sublime/blob/9df1b7c4247f8631647c7627a8da9bdc16db8b11/contracts/Pool/Repayments.sol#L300

I would expect in this case to receive a return value of zero as it's a truthful representation of the current state of the pool.

Otherwise if I were to call this from a contract I would have to wrap this function call as we do in _repayExtension which will increase costs as I need to make two calls to this contract.

https://github.com/code-423n4/2021-12-sublime/blob/9df1b7c4247f8631647c7627a8da9bdc16db8b11/contracts/Pool/Repayments.sol#L325-L335

Low risk as it may cause unexpected reverts in integrators' code but unlikely to cause any loss of funds. At the very least this can be a gas optimisation by removing the if statement in _repayExtension and replacing it with an early return for zero interest.

Recommended Mitigation Steps

Remove require statement and replace it with returning zero if there's no extension.

[ritik99]

Once an extension is repaid, isLoanExtensionActive turns false (here) because of which we do return 0 in the corresponding else block.

Whether getInterestOverdue reverts/returns 0 is honestly a matter of choice, either way does not seem to be an issue

[0xean]

Moving to non-critical