* src/libtracker-db/tracker-db-dbus.c: Some code clean ups.

	* src/libtracker-common/tracker-thumbnailer.c: When we get an
	error from the thumbnailer, include the context so we know where
	the error came from.

	* src/libtracker-db/tracker-db-manager.c:
	(function_group_concat_step): Fixed my g_return_if_fail()
	change for the g_assert() which ottela added initially, logic was
	wrong way round.

svn path=/trunk/; revision=3029