Grid image arranges tiles in wrong order if IDs in the `iref` are not sequential

libavif apparently assumes that the tile IDs of a grid image are sequential. If that is not the case, the tiles are composed into the output image in an incorrect arrangement.

Here is an [example image](https://cloud.dirk-farin.de/s/8nW38ym2DQjHBdt) that is decoded by libavif like this:

![image](https://github.com/user-attachments/assets/d5215bff-6c15-458f-835f-5ed47ae764ec)
