Visualizers with state variables throw "Index out of Bounds" error

This task is related to an older one, which I did in the old tvb-framework (before everything was put together in tvb-root) and in a Python 2 environment.

That task is this one: https://req.thevirtualbrain.org/browse/TVB-2539

You can see the exact changes I made to the code here:

https://github.com/the-virtual-brain/tvb-root/commit/2117eb3b9de85a80577f9b68cf2a1b8d8eec2503#diff-0

https://github.com/the-virtual-brain/tvb-root/commit/03e44b32b4af8a1caf0c1dcb597dd6289ae691d3#diff-0

The goal of the task would be to put that code in tvb-root and if it's needed to change some things to make it work with a python-3 environment.