trivial: Fix a uninitialized value in the dell plugin
trivial: Fix a uninitialized value in the dell plugin

Spotted using clang.

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