Gui: [skip ci] fix appearance of TaskGroups when a style sheet is set
Gui: [skip ci] fix appearance of TaskGroups when a style sheet is set

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master