_vestLock contract is not approved to transfer mainToken from PublicSale.sol contract

Handle WatchPug Vulnerability details At L225 in processWithdrawal, it calls vestLock.vest to vest 70% of the tokens bought. However, PublicSale.sol contract never approve mainToken to the vestLock contract, making processWithdrawal to revet at L225. As a result, all the withdrawals will fail and...