biasDesc just assigned in SpatialConvolution.lua not assigned in VolumetricConvolution.lua

[yanmengjia]

When I use VolumetricConvolution and VolumetricFullConvolution, it shows that biasDesc is a nil value. I have to not use noBias(), otherwise there will have a error. I found that biasDesc just assigned in SpatialConvolution.lua not assigned in VolumetricConvolution.lua, that's why I use SpatialConvolution easily but error when I use VolumetricConvolution.