src/fu-common-cab.c: fix a build warning
src/fu-common-cab.c: fix a build warning

vathpela/fwupd,vathpela/fwupd,fwupd/fwupd,hughsie/fwupd,vathpela/fwupd,hughsie/fwupd,superm1/fwupd,superm1/fwupd,fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,hughsie/fwupd,vathpela/fwupd,superm1/fwupd,fwupd/fwupd