trivial: Fix regression when switching to indexed strings
trivial: Fix regression when switching to indexed strings

When we construct a local silo we need to build the index again.

This fixes 'fwupdmgr get-details foo.cab'

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