Fixes c75ba1c7e1
```
In file included from /usr/lib/aarch64-linux-gnu/glib-2.0/include/glibconfig.h:9,
from /usr/include/glib-2.0/glib/gtypes.h:34,
from /usr/include/glib-2.0/glib/galloca.h:34,
from /usr/include/glib-2.0/glib.h:32,
from /usr/include/glib-2.0/gobject/gbinding.h:30,
from /usr/include/glib-2.0/glib-object.h:24,
from /usr/include/glib-2.0/gio/gioenums.h:30,
from /usr/include/glib-2.0/gio/giotypes.h:30,
from /usr/include/glib-2.0/gio/gio.h:28,
from ../common/flatpak-utils-http.c:23:
In function ‘glib_autoptr_clear_GFileEnumerator’,
inlined from ‘glib_autoptr_cleanup_GFileEnumerator’ at /usr/include/glib-2.0/gio/gio-autocleanups.h:69:1,
inlined from ‘flatpak_get_certificates_for_uri’ at ../common/flatpak-utils-http.c:284:34:
/usr/include/glib-2.0/glib/gmacros.h:1361:10: warning: ‘enumerator’ may be used uninitialized [-Wmaybe-uninitialized]
1361 | { if (_ptr) (cleanup) ((ParentName *) _ptr); } \
| ^
/usr/include/glib-2.0/glib/gmacros.h:1379:3: note: in expansion of macro ‘_GLIB_DEFINE_AUTOPTR_CLEANUP_FUNCS’
1379 | _GLIB_DEFINE_AUTOPTR_CLEANUP_FUNCS(TypeName, TypeName, func)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/glib-2.0/gio/gio-autocleanups.h:69:1: note: in expansion of macro ‘G_DEFINE_AUTOPTR_CLEANUP_FUNC’
69 | G_DEFINE_AUTOPTR_CLEANUP_FUNC(GFileEnumerator, g_object_unref)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
../common/flatpak-utils-http.c: In function ‘flatpak_get_certificates_for_uri’:
../common/flatpak-utils-http.c:284:34: note: ‘enumerator’ was declared here
284 | g_autoptr(GFileEnumerator) enumerator;
```
cd0212aa40