Be more defensive when remotes are missing required keys
Be more defensive when remotes are missing required keys

Fixes half of https://github.com/fwupd/fwupd/issues/2223

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