[2.0.x] Fix crash upon repeated calls to process_subcommands_now_P#10509

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

marcio-ao:pr-fix-process-subcommands-nowmarcio-ao/Marlin:pr-fix-process-subcommands-nowCopy head branch name to clipboard