The sell function of a smart contract implementation for Welfare Token Fund (WTF), an Ethereum token, has an integer overflow in which "amount * sellPrice" can be zero, consequently reducing a seller's assets.Referenceshttps://github.com/BlockChainsSecurity/EtherTokens/blob/master/ETHEREUMBLACK/sell%20integer%20overflow.mdhttps://github.com/BlockChainsSecurity/EtherTokens/tree/master/WelfareTokenFund
