I got this error message while trying to import a bvh file into blender.
Looks like your file is corrupted. NoneType means usually no data found.
You could try to import the bvh file with an earlier Blender version. 2.78 for example. When the problem still exists then you have a corrupted file.
If not then you have found a bug in the bvh addon here (imho it shouldn’t throw this error anyways, but display a regular warning instead)
Yep that was it. Thank you!