Fix: Ensure brightness >0 in ExtUI#17644

thinkyhead merged 2 commits intoMarlinFirmware:bugfix-2.0.xMarlinFirmware/Marlin:bugfix-2.0.xfrom

RudolphRiedel:bugfix-2.0.x_extuiRudolphRiedel/Marlin:bugfix-2.0.x_extuiCopy head branch name to clipboard