libostree: Fix compiler warning
libostree: Fix compiler warning

resin-io/ostree,sujitfulse/ostree,leandrosansilva/ostree,leandrosansilva/ostree,sujitfulse/ostree,leandrosansilva/ostree,GNOME/ostree,GNOME/ostree,leandrosansilva/ostree,gatispaeglis/ostree,resin-io/ostree,GNOME/ostree,resin-io/ostree,sujitfulse/ostree,GNOME/ostree,gatispaeglis/ostree,sujitfulse/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,leandrosansilva/ostree,resin-io/ostree,resin-io/ostree,GNOME/ostree,sujitfulse/ostree