Group by is not working

The async widget rendering broke the group by feature.

What we did before:

• render a group by widget with a div for the title, and a div for the content
• check if the 2 div are here
• put content in those divs

What we have now:

• render a group by widget with a div for the title, and a div for the content
• check if the 2 div are here -> they are not yet because of the asynchronicity of the rendering. We don't know when the rendering is finished