ecrecover can return undefined data if signature does not verify

Impact the ecrecover precompile does not fill the output buffer if the signature does not verify, see https://github.com/ethereum/go-ethereum/blob/b058cf454b3bdc7e770e2b3cec83a0bcb48f55ee/core/vm/contracts.goL188. however, the ecrecover builtin will still return whatever is at memory location 0...