Missing surface with GPU frustum culling on atcshd

[slipher]

r_materialSystem 1
setviewpos 688 -778 -158 -167 14

It doesn't always happen. Once again it seems to depend on the sequence of previously loaded maps. Maybe we could avoid a lot of bugs of this type by using ResetStruct on the material system data?

I'll have to see if I can find some easy to follow repro instructions, and whether it happens on other systems besides this AMD-based one.