QuickLookUISevice bug When I press the 'Mission control'-button(?) / F3, It shows me 6 extra blank windows. They're called 'QuickLookUISevice'. When I press on them nothing really happens.

Been searching for a solution, but unfortunately not able to find the right. Perhaps anyone on here knows more about this issue and is willing to tell me a little more about it. I'm quite curious how this occurs and how to fix it.

I'm running HighSierra 10.13 on a MacBook Pro
I got rid of it by force quitting it at the 'Activity Monitor'...
I'm not quite sure if this is the correct way to handle this, but it's fixed now. Still, I'd like to know how this occurs and how to handle it in the future so further responses are more than welcome.