Fix a memory leak when calling flatpak_build_file()
Fix a memory leak when calling flatpak_build_file()

Closes: #1898
Approved by: mwleeds

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