[Harry Potter] Someone's death was already spoiled in the third movie

So we all know Dumbledore dies in the sixth movie. But there are hints that his death was already spoiled in the third movie.

There is a christmas dinner with various people involved. Finally Sibyll Trelawny joins the party. Before she sits down she is frightened because there are already 12 people sitting at the table and 13 people sitting at the same table brings misery. She does not sit down and mentiones that the first of those 13 persons to stand up would die.

In order to calm her, Dumbledore stands up and leaves the table. But we later get to know that Ron's rat was just Peter Pattigrew who transformed himself. Knowing that Ron carried his rat in his pocket most of the time, that'd mean there were already 13 people at the table. As Dumbledore leaves as the first of those 13 people, his fate was sealed.