black sphere around smokey ball

so I have this smokey ball abstract art I connect the two shader but it lift me with a round sphere on the outside that I dont went please help here my blend file http://pasteall.org/blend/index.php?id=48544

I send a massage to the guy who made the video about this but just in case he didnt see it I post my problem here to here is the video https://www.youtube.com/watch?v=jBGI5Hj2vnU