flatpak_dir_find_local_related: Fix handling of subdir extensions
flatpak_dir_find_local_related: Fix handling of subdir extensions

We were not correctly handling the partial refs that ostree_repo_list_refs()
returned, instead assuming they were full refs.

Closes: #1754
Approved by: alexlarsson

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