system-helper: Plug a small memory leak
system-helper: Plug a small memory leak

g_variant_loop only takes care of memory handling if
you don't jump out of the loop.

Closes: #2371
Approved by: alexlarsson

matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak