Fix Sundowner Export

[Jacky720]

Sundowner has an undocumented chunk that is likely related to cut info. Even on the mystery-chunk branch, best efforts at editing Sundowner royally screw up his textures. This may be a separate issue, going off the incongruous material IDs used by Sundowner (two materials per mesh in many cases, but none of the IDs actually reach the total number of materials in the model).