StakingOperator::_setUnlockWindow() checks if the times are negative, which is impossible
Description
In StakingOperator::_setUnlockWindow(), unlockWindowStart and unlockWindowDuration are uint256, so they can not be negative. However, the code checks for negative values, which is a waste of gas.
Recommendation
Replace both checks by equalities to 0.
Status
Addressed in #2e77492.