[Bf-python] updates

[Jiba]

> - .getVertexInfluences(vert_index) doesn't crash Blender anymore when
> one of the linked bones is NULL. Instead of the Bone name, I first made
> it return None for NULL bones, but it makes more sense to simply not
> fill a NULL entry, since if the Bones are NULL, the vertex isn't
> influenced. 
> 
> >From what I could find debugging, the problem wasn't with multiple
> bones attached to a vertex, this worked fine.  The trouble was with
> deform groups (vertex groups): a vertex group can point to bone data,
> but one or all of these pointers may be / become NULL (and so that bone
> doesn't affect the group).  So the crashes were not caused by multiple
> influences, but rather by no influence from any or part of the bones. 
> 
> Things seem to work now, but I may be wrong and willing to keep trying
> if the issue wasn't solved yet, so feel free to email us. 

I confirm this...
The problem was related to a vertex group not used for bones animations, and not by multiple influences on a single vertex.

Thanks,
Jiba