Detect missing zero address validation.

[harshbarelia]

DappnodeSmoothingPool.claimRewards(address,uint256,bytes32[]).rewardAddress (contracts/DappnodeSmoothingPool.sol#322-324) lacks a zero-check on :

• (success) = rewardAddress.call{value: claimableBalance}(new bytes(0)) (contracts/DappnodeSmoothingPool.sol#327-329)

DappnodeSmoothingPool.initialize(address,uint256,uint256,address,uint64,uint64)._governance (contracts/DappnodeSmoothingPool.sol#183) lacks a zero-check on :

• governance = _governance (contracts/DappnodeSmoothingPool.sol#202)

DappnodeSmoothingPool.updatePoolFeeRecipient(address).newPoolFeeRecipient (contracts/DappnodeSmoothingPool.sol#612) lacks a zero-check on :

• poolFeeRecipient = newPoolFeeRecipient (contracts/DappnodeSmoothingPool.sol#614)

DappnodeSmoothingPool.initialize(address,uint256,uint256,address,uint64,uint64)._poolFeeRecipient (contracts/DappnodeSmoothingPool.sol#186) lacks a zero-check on :

• poolFeeRecipient = _poolFeeRecipient (contracts/DappnodeSmoothingPool.sol#209)

DappnodeSmoothingPool.transferGovernance(address).newPendingGovernance (contracts/DappnodeSmoothingPool.sol#545) lacks a zero-check on :

• pendingGovernance = newPendingGovernance (contracts/DappnodeSmoothingPool.sol#547)