I haven't seen the film yet, but from what I have heard, am I right in saying that Dumbledore didn't have a gross blackened hand which was was caused by the ring that had the horcrux in it, which would have caused him to die anyway.
(SPOILER)It is one of the main reason why he got Snape to kill him. So why leave it out. it would have been an extra 5 mins in make up and its not like he ever explains to harry what happened to it so it would have added much more film time.