FIX Correctly handle NaNs in `VertexRGB` and `VolumeRGB` (#458)
FIX Correctly handle NaNs in `VertexRGB` and `VolumeRGB` (#458)

* FIX nans in VertexRGB

* Actually mask out nans

* Implement Tom's suggestions

* Access data directly instead of private property

* FIX make 1d alpha

* Try fixing alpha for VolumeRGB too

* FIX color_voxels handles nans by returning an appropriate alpha
gallantlab/pycortex,gallantlab/pycortex,gallantlab/pycortex,gallantlab/pycortex,gallantlab/pycortex