trivial: Fix a compile warning when there is no polkit
trivial: Fix a compile warning when there is no polkit

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