Sliders sometimes still visible in next slide

[danibene]

Hi, thank you very much for making OpenMATB available :)

I noticed that for some questionnaires I added, the sliders from the previous slide were still visible in the next slide:

This is how I was able to fix it for my case: https://github.com/juliencegarra/OpenMATB/compare/master...danibene:OpenMATB:change/remove_previous_sliders?expand=1

I'd be happy to open a PR if you are interested, and I'm also open to any suggestions in case there might be a better way to go about addressing this issue.