Leaflet groupedLayers control without checkbox

In my Leaflet L.control.groupedLayers block there is a list of map markers filters similar to http://leafletjs.com/examples/wms/wms-example3.html but with checkboxes instead of radio input elements, everything is working.

Now, I want to add a button which will disable filters by unchecking all checkboxes. I implemented such button and it works besides one thing — there is a checkbox from the left to the button:

The question:
How can I get rid of such checkbox or at least hide it?