[gnome-photos] thumbnailer: Assert that the skeleton's lifetime is sane

[Debarshi Ray <debarshir src gnome org>]

commit b50eb8d7680e5af97c3695dd607bcde63eab65f3
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Jun 8 15:40:42 2017 +0200

    thumbnailer: Assert that the skeleton's lifetime is sane
    
    Clearing the reference during dispose might mask an actual bug.
    
    The skeleton should be instantiated in the dbus_register virtual
    method, which is expected to be called only once. If instantiated, it
    should then be torn down in dbus_unregister, which might be invoked
    more than once.

 src/photos-thumbnailer.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/photos-thumbnailer.c b/src/photos-thumbnailer.c
index e7dbcbb..cec79c0 100644
--- a/src/photos-thumbnailer.c
+++ b/src/photos-thumbnailer.c
@@ -672,6 +672,8 @@ photos_thumbnailer_dbus_register (GApplication *application,
   GDBusAuthObserver *observer = NULL;
   gboolean ret_val = FALSE;
 
+  g_return_val_if_fail (self->skeleton == NULL, FALSE);
+
   if (!G_APPLICATION_CLASS (photos_thumbnailer_parent_class)->dbus_register (application,
                                                                              connection,
                                                                              object_path,
@@ -780,8 +782,9 @@ photos_thumbnailer_dispose (GObject *object)
 {
   PhotosThumbnailer *self = PHOTOS_THUMBNAILER (object);
 
+  g_assert_null (self->skeleton);
+
   g_clear_object (&self->connection);
-  g_clear_object (&self->skeleton);
   g_clear_pointer (&self->cancellables, (GDestroyNotify) g_hash_table_unref);
   g_clear_pointer (&self->resource_gegl, (GDestroyNotify) g_resources_unregister);