ostree_sysroot_upgrader_finalize: free new_revision

Leak found with valgrind memcheck.

Signed-off-by: Simon McVittie <smcv@debian.org>

Closes: #556
Approved by: cgwalters

src/libostree/ostree-sysroot-upgrader.c

@@ -188,6 +188,7 @@ ostree_sysroot_upgrader_finalize (GObject *object)
   g_free (self->origin_remote);
   g_free (self->origin_ref);
   g_free (self->override_csum);
+  g_free (self->new_revision);
 
   G_OBJECT_CLASS (ostree_sysroot_upgrader_parent_class)->finalize (object);
 }