gio-querymodules: fix memory leak

Spotted thanks to ASAN.

https://bugzilla.gnome.org/show_bug.cgi?id=778207

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

gio/gio-querymodules.c

@@ -119,6 +119,7 @@ query_dir (const char *dirname)
         g_printerr ("Unable to unlink %s: %s\n", cachename, g_strerror (errno));
     }
 
+  g_free (cachename);
   g_string_free (data, TRUE);
 }