[BUG] bulkTransfer always returns false

[YoshihitoAso]

1. Describe the bug

• The return value of bulkTransfer is always false.

        bool result = false;
        for(uint i = 0; i < _toList.length; i++) {
            if (isContract(_toList[i])) {
                result = transferToContract(_toList[i], _valueList[i], empty);
            } else {
                result = transferToAddress(_toList[i], _valueList[i], empty);
            }
            if (result == false) {
                success = false;
            }
        }
        return success;

2. Expected behavior

• It returns true when the process finishes successfully.