Js error displayed in console for Brain Viewer portlet.

Steps:
1. Go to the Simulator page
2. Press on the button 'Configure View' from the right part of the page.
3. Select 'Brain Viewer' portlet.
4. Press 'Save choices' button.
5. Launch the simulation.
6. After the simulation is finished, press on the + button to maximize the portlet view.

If we open the browser console we can see the following exception:

Uncaught TypeError: Cannot read property 'style' of null brainLegend.js:195