httpcache: Free the GError before exiting

Signed-off-by: Simon McVittie <smcv@collabora.com>

tests/httpcache.c

@@ -6,7 +6,7 @@ int
 main (int argc, char *argv[])
 {
   g_autoptr(FlatpakHttpSession) session = flatpak_create_http_session (PACKAGE_STRING);
-  GError *error = NULL;
+  g_autoptr(GError) error = NULL;
   const char *url, *dest;
   int flags = 0;