处理签名字典出错，详细信息：Object reference not set to an instance of an object.

[AndHuang]

private ZPayRsaAssist GenerateRsaAssist(ZPayConfig config)
{
if (ConfigMode==ConfigProviderMode.Context)
return new ZPayRsaAssist(config.AppPrivateKey, config.AppPublicKey, config.Charset);

        if (_rsaAssist==null)
            return _rsaAssist= new ZPayRsaAssist(config.AppPrivateKey, config.AppPublicKey, config.Charset);
        
        return _rsaAssist;
    }

定位：if (ConfigMode==ConfigProviderMode.Context)这行代码中的ConfigMode为空