trivial: fu-tool: fix a crash with `--cleanup`
trivial: fu-tool: fix a crash with `--cleanup`

vathpela/fwupd,vathpela/fwupd,hughsie/fwupd,vathpela/fwupd,vathpela/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd